Preheat oven to 325°F (160°C). Line two cupcake pans with paper liners.

In a medium bowl, whisk together flour, baking powder, and salt.

In a stand mixer, cream butter and sugar until light and fluffy (3-5 minutes).

Beat in eggs one at a time, scraping the bowl after each addition.

Mix in lime zest, lime juice, and vanilla extract.

Gradually add dry ingredients alternating with buttermilk, beginning and ending with dry ingredients.

Divide batter evenly into cupcake liners, filling each about 3/4 full.

Bake for 12-15 minutes, or until a toothpick inserted into the center comes out clean.

Let cupcakes cool in the pan for a few minutes, then transfer to a wire rack to cool completely.

For the frosting: Whip butter until light and fluffy.

Gradually add powdered sugar, mixing until smooth.

Add lime zest and margarita mixer.

Blend until smooth, adding more margarita mixer as needed.

Add green and yellow food coloring, if desired.

Frost cooled cupcakes.

Garnish with lime zest, sprinkles, or lime slices.