A tangy citrus flavored cupcake filled with key lime curd will be a welcome addition and soon become your new favorite cupcake and go to dessert. Key lime cupcakes are a sour cream butter cupcake flavored with key lime juice and almond, cored and filled with key lime curd, then topped with buttercream and graham cracker crumbs.
You can say I’m crazy about these Key Lime Cupcakes filled with Key Lime curd, they are so tangy. First, the pale green cupcakes look so pretty and then when you bite into it, you get a big dollop of Key Lime Curd.
Spring is the perfect time of year for this creative cupcake recipe, you should find plenty of citrus to use, like for these Lemon Cupcakes or lemon bars. Here is an informative article in case you wanted to know the difference between limes and key limes.
Quick Look
- 🕒 Prep Time: 10 minutes
- 🌡️ Cook Time: 18 to 20 minutes
- ⏳ Total Time: 30 minutes
- 🍽️ Serving: 16 to 18 cupcakes
- ⚡ Calories: 475kcal per frosted cupcake
- 🌶️ Flavor Profile: Sharp key lime and a touch of almond against a rich sour cream crumb
- ✋ Difficulty: Moderate, the folded egg whites and the filling are the only fussy parts
Quick Answer
Cream the butter and sugar until well blended, then beat in the flavoring and egg yolks. Mix in the sour cream and fold in the dry ingredients. Beat the egg whites separately until fluffy, not stiff, and fold them into the batter without overmixing. Fill paper cups two thirds full with an ice cream scoop and bake at 350 degrees for 18 to 20 minutes until light golden. For the frosting, beat softened butter with sifted powdered sugar a cup at a time, add the extracts and salt and beat 3 to 5 minutes. Once the cupcakes are cool, fill them with key lime curd, frost, and dust with graham cracker crumbs and key lime zest.
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Why This Recipe Works
Click to see the technique science
- Yolks and whites go in separately. The yolks bring richness into the creamed butter, and the whites are beaten and folded in at the end for lift. Whole eggs would give you a denser, flatter cupcake.
- Fluffy, not stiff. Whites beaten to stiff peaks break into lumps when you fold them and leave streaks. Fluffy whites fold in smoothly and still carry air.
- Sour cream is the tenderizer. The fat and the acid together keep the crumb soft and give the cupcake enough tang to stand up to the curd.
- Almond flavor behind the lime. A teaspoon of almond extract reads as depth rather than as almond, and it keeps the lime from tasting thin.
- Key lime, not regular lime. Key limes are sharper and more floral. Nellie and Joe’s bottled juice is consistent year round, which matters when fresh key limes are out of season.
- The graham cracker crumbs are not decoration. They put key lime pie on top of the cupcake, which is what the whole thing is referencing.
- An ice cream scoop fills the liners evenly. Uneven cupcakes bake unevenly, and two thirds full is the line between a domed top and a spill.
Why You’ll Love This Recipe
- The surprise in the middle. The pale green cupcakes look so pretty, and then when you bite into it you get a big dollop of key lime curd.
- Properly tangy. These are not sweet cupcakes with a hint of lime. The curd and the juice both push the sour side.
- They photograph beautifully. Pale green against white frosting with graham crumbs and zest on top.
- Perfect for a tea party. These treats would also be perfect for your next tea party, and they sit well with my tea party cupcakes.
- Spring citrus. Spring is the perfect time of year for this recipe, when you can find plenty of citrus.
- It makes 16 to 18. Enough for a party, or for a tiered tray alongside my lemon bars.
Key Ingredients
A cupcake list and a frosting list, and the key lime juice is the one worth buying properly. Quantities are in the recipe card below.
- Butter. Half a pound at room temperature for the cupcakes and another half pound softened for the frosting.
- Key Lime Juice. Nellie and Joe’s is what I use. Key limes are sharper than regular limes, and the bottled juice is consistent all year.
- Egg Yolks and Egg Whites. Four of each, used separately. The yolks go into the batter and the whites are beaten and folded in.
- Sour Cream. One cup, for a tender crumb and a little extra tang.
- Almond Flavor. One teaspoon. It sits behind the lime and rounds it out.
- Sifted Flour, Baking Soda and Salt. Sifted matters, since the batter is folded rather than beaten once the dry goes in.
- Powdered Sugar. Three cups, sifted, added to the frosting one cup at a time.
- Lime Oil or Key Lime Juice in the frosting, to taste.
- Graham Cracker Crumbs. A quarter cup, dusted on top, which is what makes them read as key lime pie.
- Key Lime Curd for the filling. Use a citrus zester on key limes over the graham crackers to finish.
See the recipe card below for exact quantities and full instructions.
Variations & Substitutions
Most of these are how I serve them rather than how I bake them.
- Make them mini. I like to use mini cupcakes for my tea parties and I put 3 small desserts on a plate. I usually place a cupcake, maybe a chocolate dipped strawberry and then either a cookie or a mini cheesecake.
- Swap the citrus. The same cupcake works with lemon curd instead, which is essentially my lemon curd cupcakes.
- Skip the filling. Frosted and dusted with graham crumbs they are still very good, and a lot faster.
- Regular limes in a pinch. Persian limes are milder and less floral, so use a little more juice.
- Add zest to the frosting. A little key lime zest beaten in turns the buttercream pale green without any coloring. My frosting notes cover getting a clean swirl.
- Leave out the almond. If almond is not your thing, vanilla works, the flavor is just flatter.
How to Make Key Lime Cupcakes
- Cream the butter and add the sugar, beating until well blended. Add the flavoring and egg yolks to the butter mixture and beat well.
- Add the sour cream and mix well. Fold in the dry ingredients. When incorporated, remove from the mixer and set aside.
- Beat the egg whites in a clean bowl until fluffy, not stiff. Fold them into the batter until well mixed. Do not overmix.
- Heat the oven to 350 degrees and use an ice cream scoop to fill paper cups two thirds full. Bake for 18 to 20 minutes, until light golden.
- For the frosting, beat the softened butter with the sifted powdered sugar, one cup at a time. Add the extracts and salt and beat for 3 to 5 minutes. Add more extract to taste.
- Once the cupcakes have cooled, fill them with key lime curd and frost.
- Optional: dust with graham cracker crumbs.
- Using a citrus zester, zest key limes on top of the graham crackers.
Recipe Tips & Tricks
- Beat the whites fluffy, not stiff. This is the one step that decides the texture.
- Fill two thirds full with an ice cream scoop so every cupcake bakes at the same rate.
- Cool completely before filling. Warm cupcakes turn curd into a puddle.
- Core them with an apple corer or a small knife, taking a plug out of the middle and keeping the top to set back on.
- Sift the powdered sugar. Three cups of unsifted sugar will leave lumps no amount of beating removes.
- Dust the graham crumbs just before serving so they stay crisp on the frosting.
Serving Ideas & Suggestions
These treats would also be perfect for your next tea party. I like to use mini cupcakes for my tea parties and I put 3 small desserts on a plate. I usually place a cupcake, maybe a chocolate dipped strawberry and then either a cookie or a mini cheesecake. My tea party checklist covers the rest of the table, and there are menus in my tea party cupcakes, garden tea party, afternoon tea and tea party desserts posts.
If you like key lime cupcakes you might also enjoy my mint chocolate chip cupcakes in a jar, key lime smoothie, lemon curd cupcakes and key lime cheesecake. For a birthday table put them next to my vanilla birthday cupcakes or my Earl Grey cupcakes, and there are more flavors in my 25 gourmet cupcake recipes. If you are working through a bag of citrus, my what to do with lemons post and my notes on how to zest will both help, and my strawberry cheesecake in a jar is the other dessert I bring to spring parties.
Key Lime Cupcake FAQs
Key limes are smaller, sharper and more floral than the Persian limes sold in most grocery stores. If you use regular limes here the cupcakes will be milder, so add a little extra juice.
Yes, and I do. Nellie and Joe’s is what this recipe was written with. Bottled juice is consistent year round, which matters because fresh key limes are seasonal and small enough to be a chore to juice.
Cut a plug out of the center of each cooled cupcake with an apple corer or a small knife, spoon in the key lime curd, and set the top of the plug back on before you frost. The frosting hides the seam.
The whites are what lift this batter. Beaten fluffy and folded in at the end, they keep the cupcake light in spite of the butter and sour cream. Beat them fluffy, not stiff, or they will not fold in cleanly.
Because of the curd, keep them in the refrigerator in an airtight container for up to three days. Let them sit out for 20 minutes before serving so the butter in the frosting softens.
Yes. Bake the cupcakes a day ahead and keep them unfilled and unfrosted in an airtight container, then fill and frost the day you serve them. Unfrosted cupcakes also freeze well for up to two months.
Key Lime Cupcakes filled with Key Lime Curd
Ingredients
Cupcakes
- 1/2 lb of butter room temp
- 1 1/2 cups of white granulated sugar
- 4 large egg yolks
- 1 cup of sour cream
- 2 cups sifted flour
- 1 Teaspoon baking soda
- 1/8 teaspoon salt
- 1 teaspoon key lime juice (Nellie and Joe’s)
- 1 teaspoon almond flavor
- 4 large egg whites beaten fluffy not stiff
Frosting
- 1/2 lb of softened butter
- 3 cups of sifted powdered sugar
- 1 Tablespoon of vanilla extract
- 1 teaspoon of lime oil or Key lime juice to taste
- 1/8 teaspoon of salt
- 1/4 cup graham cracker crumbs
Instructions
- Cream butter and add sugar beating until well blended. Add flavoring and egg yolks to butter mixture and beat well.
- Add sour cream and mix well. Fold in dry ingredients. When incorporated remove from mixer and set aside.
- Beat egg whites in a clean bowl until fluffy. Fold into the batter until well mixed. Do not over mix.
- Heat oven to 350 degrees and use an ice cream scoop to fill paper cups 2/3 full. Bake for 18 – 20 minutes until light golden.
Frosting
- Beat softened butter with sifted powdered sugar, 1 cup at a time. Add extracts and salt. Beat for 3 – 5 minutes. Add more extract to taste.
- Fill with Key Lime Curd and frost when cupcakes have cooled.
- Optional: Dust with graham cracker crumbs
- Using a citrus zester, zest key limes on top of graham crackers
amygm says
Oh wow, these look just scrumptious! I love Key Limes!
Candi says
They are so delicious Thanks for stopping by.
Francene says
This sound so delicious. Great flavor.
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singlemotherahoy says
What is the difference between key limes and… just limes?
Sorry, I'm British and also rather uncultured. I've always wondered!
Stopping by from Ultimate Blg Challenge!
Candi says
They are smaller and a little more tart.
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May says
Wow, these look delicious! I can't wait to make some of these. I'm stopping by from the Gingham & Roses link up!
Cindy Howell says
This look really yummy! I love lime flavor, even in desserts.
Thank you so much for sharing at last week's Super Saturday Afternoon Tea Link-Up!!!
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Theresa says
Hi Candi, I love Key Lime! And cupcakes are one of our favorite treats, yet I haven't made Key Lime cupcakes yet. Pinning to my baking board to try your recipe this spring.
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Audrey says
Candi, I love anything key lime. These cupcakes look delicious. I am sharing them on Facebook—maybe Amy will make them for me, but I’m thinking that I may not be able to wait that long so I may have to make them myself!