Key Lime Cupcake Recipe

My key lime cupcakes are definitely an office favorite. I end up making these multiple times a year. Of course out of all the cupcakes in my recipe catalog, these are one of my least favorite to make. The people that usually request these are just lucky I like them a lot!

Below are two frosting recipes – I rarely ever make the cream cheese version of the frosting but instead, opt for a plainer vanilla frosting. Baker’s choice! The cupcakes pictured here were a birthday treat for one of my IT support people.

Key lime cupcakes with vanilla frosting, green sugar crystals and lime flavored Peeps

Key lime cupcakes with vanilla frosting, green sugar crystals and lime flavored Peeps.



1 3/4 cups all-purpose flour
1 tsp baking powder
1/2 tsp baking soda
1/2 tsp salt
1 cup full-fat sour cream
1/2 cup unsalted butter, at room temperature
1/2 cup granulated sugar
1/4 cup light brown sugar
1/2 tsp key lime extract
1 egg plus one egg yolk, at room temperature
1 1/2 tbsp fresh key lime juice

Preheat oven to 350°. In a medium bowl combine the flour, baking powder, baking soda, and salt; whisk well and set aside. In a large bowl, beat the butter on medium speed until smooth and creamy, about 30 seconds. Add in both sugars and lime extract and beat until well combined. Add in the egg and egg yolk and mix well. Reduce the mixer speed to low. Add in 1/2 of the flour mixture and mix until just combined. Add 1/2 of the sour cream and mix until just combined. Repeat with remaining flour and sour cream, being sure to mix on low until just combined. Turn mixer off. Using a rubber spatula, quickly fold in the lime juice. Bake for 16-18 minutes, or until a toothpick inserted in the center comes out clean.

Cream Cheese Frosting

1/2 cup unsalted butter, softened
8 ounce block full-fat cream cheese, softened
4 1/2 cups powdered sugar
1/4 tsp salt
1 1/2 tbsp fresh key lime juice
1/4 tsp key lime extract

In a medium bowl, beat the butter and cream cheese on medium-speed until smooth and creamy. Reduce the speed to low and slowly add in the powdered sugar and lime juice, beating until light and fluffy, about 2 minutes. Add in the salt, key lime juice and extract; beat smooth.

Vanilla Frosting

3 cups powdered sugar
1/3 cup butter or margarine, softened
1 1/2 tsp vanilla
1 to 2 tbsp milk

In a medium bowl, beat powdered sugar and butter. Stir in vanilla and 1 tablespoon of the milk. Gradually beat in just enough remaining milk to make frosting smooth and spreadable.

My notes:

  • The order in which you combine and introduce ingredients matters. My first attempt to dump everything in at once failed miserably. Make sure you follow the directions closely!
  • Temperature matters! I can’t stress this enough! If I have indicated that something should be softened or at room temperature there is an important reason for it. I am all about as many short cuts as possible, but it will mess up the batter and/or frosting consistency if you don’t play by the rules.
  • If you don’t want an overpowering key lime flavor I recommend a plain frosting like the vanilla above, if you want to punch someone in the face with flavor then, by all means, go for the key lime cream cheese frosting.
  • The lime peeps happened to be available as it was Easter time, but some other options for garnish can be a lime twist, zest or graham cracker crumbs.
  • I prefer to use the extract for a more definitive flavor in the cupcakes. I used to use some ridiculously expensive extract because it worked well and I liked the flavor, but I recently found a much more inexpensive brand that has a better flavor from LorAnn Oils. I order it right off of Amazon, and since I have Prime I get the 2 day shipping for free. If you want a 30 day free trial click here.