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I figured one of these days I’d have a go at key lime pie or something, so I bought 10 limes. And then, I just never got around to it… So I decided to use one of those limes for lime cupcakes expect those cupcakes didn’t rise properly and they were too dense (although the flavoring was really good!). Yesterday, I made yellow cupcakes using sour cream for James and Suki’s bday and decided to use the limes for frosting.

I ended up running out of confectioner’s sugar and having used way too much better (relative to confectioner’s sugar), I threw the incomplete frosting into the fridge and went to the supermarket. When I came back, the frosting had separated, even after adding the proper amounts of sugar. I wouldn’t say that it curdled, but it was as if beads of sugar wouldn’t integrate properly into the frosting.

So, I found a way to salvage it. I added half a slab of room temperature cream cheese (make sure it’s at room temperature or else it’ll also separate) and viola! Good as new. If the frosting does curdle, just whisk it over a freezing water bath and it should be okay. But if it’s just separated and lumpy, add cream cheese.

The cupcakes were delicious and the lime frosting wasn’t anything over the top- it just had that lime tang to it. All I used was lime zest (lime juice will make frosting curdle).

Yellow Sour Cream Cupcakes

(taken from Barefoot Contessa, makes 24 cupcakes)

  • 18 tablespoons unsalted butter
  • 3 cups sugar
  • 6 extra large eggs (room temp)
  • 1 cup sour cream (room temp)
  • 1 1/2 teaspoons vanilla extract
  • 3 cups all-purpose flour
  • 1/3 cup cornstarch
  • 1 teaspoon salt
  • 1 teaspoon baking soda


  1. Preheat oven to 350° and insert paper liners in muffin tins.
  2. Cream butter and sugar until light and fluffy, then add eggs two at a time on medium speed of electric mixer.
  3. Add sour cream and vanilla.
  4. Sift together dry ingredients and with mixer on low speed, add to the butter mixture.
  5. Mix just until combined.
  6. Fill cupcake liners to the top with batter and bake for 20 minutes or until a toothpick inserted in the center comes out clean.
  7. Cool to room temperature on a wire rack.
Lime Frosting


  • 2 (8 ounce) packages cream cheese, softened
  • 1/2 cup butter, softened
  • 2 cups sifted confectioners’ sugar
  • 1 teaspoon vanilla extract
  • 1 tablespoon lime zest
  • Green food coloring (optional)

Frosting Recipe:

  1. Cream the butter and confectioners’ sugar together until creamy. Then add the vanilla extract
  2. Zest a lime (about a tablespoon) over the frosting and combine

Side Notes:

  • For the food coloring, use the gel types because they’re so concentrated that you only need a drop or so
  • As mentioned before, make sure everything is at room temperature, especially for the frosting. If both aren’t at room temperature, the butter and cream cheese will curdle
  • Zest a lime over the bowl and combine with food coloring
  • The frosting recipe above is for a real cream cheese frosting. I had initially set out using a buttercream frosting and then added cream cheese (the ingredients are basically the same anyway)