The key lime cupcakes have more of a tangy flavor and it’s not too sweet, that’s why I love thee cupcakes. It has a lime cupcake base topped with Swiss meringue buttercream. Crack two eggs into a bowl then add sugar and zest a lime then juice the lime into the bowl. Give everything a whisk until well combined. In a small saucepan, heat an inch of simmering water then place the bowl right on top making sure the heating water does not touch the bowl.

Whisk the mixture in the bowl until it starts to thicken up then remove from the heat, add more lime zest and butter then give it a quick whisk to melt the butter. Transfer the lime curd into a shallow dish so it can cool in the refrigerator. To make the swiss meringue buttercream, add sugar to egg whites in a bowl then give that a whisk until well combined then like we did with the lime curd, place the bowl over a pot of simmering water and whisk that until smooth and milky.

Transfer it to a stand mixer and lift it on high speed for a couple of minutes until glossy. Add room temperature butter, vanilla extract beat t then set it aside. In a different bowl, sift cake flour and all-purpose flour, baking powder and salt then set aside. Beat butter and sugar in a different bowl then add in eggs, vanilla extract and lime zest then begin adding the flour mixture and start combing the mixture.

Add lime juice to the mixture with a third cup of milk and mix them until the cupcake batter is well-formed. Transfer the batter into cupcake liners then bake them at 350 Fahrenheit for 15 to 18 minutes. Take the lemon curd out of the fridge and transfer it to a pastry bag and once the cupcakes are baked, use an apple corer to core the center of the cupcakes and fill it with lemon curd. Once done, take the swiss meringue buttercream and pip it on top of the cupcakes.


Lime Curd;

  • 2 eggs
  • 1/2 cup(115 grams) sugar
  • heaping 1/3 cup lime juice
  • 1 tbsp lime zest
  • 3 tbsp (43 grams) butter

Swiss Meringue Buttercream;

  • 4 egg whites
  • 1 1/2 (340 grams) cup sugar
  • 1 cup (2287 grams) softened unsalted butter
  • 1 tsp vanilla extract

Lime Cupcakes;

  • 1 cup (115 grams) of cake flour
  • 1/2 cup(64 grams) all-purpose flour
  • 1 1/2 tsp baking powder
  • 1/4 salt
  • 1/2 cup softened unsalted butter
  • 3/4 cup (150 grams) sugar
  • 2 eggs
  • 1 1/2 tsp vanilla extract
  • 2 tbsp lime zest
  • 1/4 cup lime zest
  • 1/3 cup milk


  1. Preheat the oven to 350°F and prepare a cupcake pan with cupcake liners.
  2. In a large mixing bowl, cream the butter and sugar together until light in color and fluffy, about 3-4 minutes.
  3. Add sour cream, vanilla extract, and key lime zest and mix until well combined.
  4. Add egg whites in two batches, mixing until well combined after each.
  5. In a separate bowl, whisk together flour, baking powder, and salt.
  6. In a separate small measuring cup, combine the milk and key lime juice.
  7. Add half of the dry ingredients to the batter and mix until well combined.
  8. Add the milk mixture and mix until well combined. Add remaining dry ingredients and mix until well combined.
  9. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated.
  10. Fill the cupcake liners about three-quarters full. Bake for 15-17 minutes, or until a toothpick inserted comes out with a few crumbs.
  11. Remove cupcakes from oven and allow to cool for 2-3 minutes, then remove to a cooling rack to finish cooling.

Make the Lime Buttercream Frosting;

  1. In a large mixing bowl, combine the butter and shortening with a mixer until smooth.
  2. Add about half of the powdered sugar and mix until smooth and well combined.
  3. Add the key lime zest and 3 tablespoons of key lime juice and mix until combined.
  4. Add the remaining powdered sugar and mix until smooth. Add additional key lime juice, as needed to reach desired consistency.
  5. Pipe the frosting onto the cupcakes using a large round pastry tip, like this one.
  6. Press graham cracker crumbs around the bottom edge of the frosting.