Margarita Cupcakes

Ingredients

• 9 ounces margarita mixer, bottled liquid
• 3 ounces tequila
• 3/4 ounce grand marnier
• 1 (18.25 ounce) box white cake mix
• 3 large egg whites
• 2 tablespoons canola oil
• 1 tablespoon lime zest
• 1 cup unsalted butter, at room temperature
• 5 to 6 cups powdered sugar
• 2 tablespoons lime juice, freshly squeezed
• 1/8 teaspoon salt
• 1 teaspoon lime zest
• green food coloring, if desired
• small lime slices for garnish, if desired