Preparation Steps

• Stir together the coarse sea salt, granulated sugar, and extra lime zest for garnish; rub the zest into the salt and sugar with your fingertips until fragrant. Spread on a small plate to dry slightly.
• Heat the oven to 350°F. Line two 12-cup muffin tins with paper liners.
• In a large bowl, whisk the cake mix with the kosher salt, 1 tbsp lime zest, and orange zest to evenly distribute the citrus oils.
• In a separate bowl or large measuring jug, whisk the eggs, margarita mix, vegetable oil, and vanilla until smooth and slightly frothy.
• Pour the wet mixture into the dry ingredients and stir with a spatula just until no dry pockets remain. Let the batter rest for 5 minutes to hydrate and thicken.
• Scoop the batter into liners, filling each about two-thirds full. Bake 17–20 minutes, rotating the pans halfway through, until the tops spring back and a toothpick comes out clean or with a few moist crumbs.
• Cool in the tins for 10 minutes, then transfer cupcakes to a rack and cool completely before frosting.
• Make the frosting: Beat the softened butter on medium speed for 1 minute until creamy. Add about half the powdered sugar and beat on low until incorporated. In a small cup, combine tequila, lime juice, and 1 tsp lime zest.
• With the mixer running, drizzle in half of the tequila–lime mixture, then add the remaining powdered sugar. Beat on medium-high for 2 minutes. Add the remaining tequila–lime mixture and the pinch of fine salt; whip 1 more minute until light and fluffy. If the frosting seems soft, chill it for 10 minutes before using.
• Frost the cooled cupcakes with a piping bag or an offset spatula. Immediately dip just the outer edge of the frosting into the salt–sugar–zest mixture to create a cupcake “salt rim,” or lightly sprinkle it over the top. Serve at room temperature.