Preheat your oven to 350°F (175°C). Line a cupcake pan with cupcake liners to prevent sticking.

In a large mixing bowl, cream together the softened butter and granulated sugar using an electric mixer on medium speed until light and fluffy, about 3-4 minutes. This incorporates air into the mixture, helping the cupcakes rise.

Add the eggs one at a time, mixing well after each addition. This ensures that the eggs are fully incorporated and helps with the structure of the cupcakes.

In a separate bowl, whisk together the flour, baking powder, baking soda, and salt. This helps to evenly distribute the leavening agents.

Gradually add the dry ingredients to the butter mixture, alternating with the buttermilk, lime juice, tequila, and vanilla extract. Begin and end with the dry ingredients. Mix until just combined; overmixing can lead to dense cupcakes.

Fold in the lime zest gently using a spatula.

Spoon the batter into the prepared cupcake liners, filling each about 2/3 full to allow room for rising.

Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center comes out clean. This ensures the cupcakes are fully baked.

Remove from the oven and let them cool in the pan for 5 minutes before transferring to a wire rack to cool completely.

In a large mixing bowl, beat the softened butter with an electric mixer until creamy.

Gradually add the powdered sugar, mixing on low speed until combined. This prevents a sugar cloud from forming.

Add the lime juice, lime zest, and vanilla extract. Beat on medium speed until the frosting is light and fluffy, about 3-5 minutes.

If the frosting is too thick, add a teaspoon of milk at a time until the desired consistency is reached.

Once the cupcakes are completely cool, use a piping bag fitted with a star tip to frost each cupcake generously with the lime frosting.

To garnish, rim the tops of the frosted cupcakes with coarse sea salt and place a lime slice on each one for decoration.