Preheat the oven to 350°F (176°C) and line a 6 cup pan with cupcake liners.

Whisk the flour, baking powder, and salt together in a small bowl.

In a medium bowl, whisk the melted butter, sugar, egg, vanilla, lime zest, lime juice, and 1tbsp of tequila together until combined.

Stir in about half of the flour mixture. Then stir in the milk and the rest of the flour mixture and mix until fully combined. The batter will be thin.

Pour about 1/4 cup of batter into each cupcake liner (they should be about 3/4 full)

Bake for 16 minutes or until a toothpick comes out clean. Remove from cupcake pan. Pour 1/2 tbsp of tequila into a small bowl and using a pastry brush, lightly brush the tops of the warm cupcakes. Let cupcakes cool completely before frosting.

In a mixing bowl, cream together the softened butter and cream cheese until completely smooth. Then add in the powdered sugar and beat on slow until combined. Slowly add in the lime juice, tequila, and salt until fully combined. Continuously beating for 3 minutes on high speed until light and fluffy.

Frost cooled cupcakes. Garnish with lime slices and lime zest.