Preheat and Prepare: Preheat the oven to 300°F and line a cupcake pan with liners. Using a slightly lower temperature helps keep the cupcakes light and tender.
Cream Butter and Sugar: Beat the butter and granulated sugar together until pale and fluffy, about 2 minutes, scraping down the bowl as needed.
2 sticks unsalted butter, 2 cups granulated sugar
Add Eggs and Lime: Add the eggs one at a time, mixing well after each addition, then stir in the lime zest so the citrus flavor is evenly distributed.
6 large eggs, 2 tablespoons lime zest
Mix the Batter: Add the milk, flour, baking powder, and salt. Mix on low speed just until combined, then briefly increase to medium speed to smooth out the batter.
½ cup milk, 3 cups all-purpose flour, 1 tablespoon baking powder, ½ teaspoon salt
Color the Batter: Add a few drops of green food coloring if using and mix until you reach a soft lime-green color. This step is optional and purely visual.
Green food coloring
Fill and Bake: Fill the cupcake liners about three-quarters full with batter and bake for 20 to 22 minutes, rotating the pan halfway through, until a toothpick inserted in the center comes out clean.
Cool Completely: Transfer the cupcakes to a wire rack and let them cool completely before adding the frosting.
Make the Frosting Base: Beat the butter, strawberry syrup, vanilla extract, and tequila until smooth and fluffy. For a non-alcoholic version, omit the tequila or replace it with milk, lime juice, or clear vanilla extract.
1 cup unsalted butter, 6 tablespoons strawberry syrup, 1 teaspoon vanilla extract, 2 tablespoons tequila
Adjust Consistency: Add the powdered sugar gradually, mixing until the frosting is smooth, thick, and easy to pipe. If the frosting is too soft, add more powdered sugar one tablespoon at a time.
3½ cups powdered sugar
Frost and Garnish: Pipe the frosting onto the cooled cupcakes and garnish with lime wedges if desired. Serve immediately or chill briefly to help the frosting set.
Lime wedges