First, zest the limes and juice the zested limes for the recipe. Set to the side.
Next, preheat the oven to 325 degrees Fahrenheit.
In a medium bowl, combine the flour, baking powder and salt; stir with a whisk to blend.
Using a KitchenAid Stand Mixer fitted with the paddle attachment, cream together the butter and sugar on medium-high speed until light and fluffy, 3-5 minutes. Add in the eggs one at a time, mixing well after each addition and scraping down the sides of the bowl as needed.
Beat in the lime zest, lime juice and vanilla. With the mixer on low speed, alternate by mixing in the dry ingredients and buttermilk. Beat each addition just until incorporated.
Place cupcake liners in cupcake baking pan. Using a large cookie scoop, scoop batter into the cupcake liners, filling each about ¾ full. Bake 20-24 minutes, or until a toothpick inserted in the center comes out clean.
Let cool in the pan 5-10 minutes, then transfer to a wire rack to cool completely.
Last, brush the cooled cupcakes with 1-2 tablespoon of tequila to emphasize the true margarita flavor.