Preheat your oven to 350°F. Line a standard muffin tin with cupcake liners.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy, about 3-4 minutes.
Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract, buttermilk, lime juice, lime zest, and tequila until combined.
Gradually add the dry ingredients to the wet mixture, mixing just until combined. Do not overmix.
Divide the batter evenly among the cupcake liners, filling each about 2/3 full. Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cupcakes to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.
For the frosting, beat the softened butter in a mixing bowl until creamy. Gradually add the powdered sugar, mixing on low speed until combined.
Add the lime juice, lime zest, tequila, and a pinch of salt. Beat on high speed for 2-3 minutes until the frosting is light and fluffy.
Once the cupcakes are completely cool, frost them generously with the tequila lime frosting.