How to Make It
Prepare the Cake Layers: Preheat oven to 350°F. Stir together cake mix, gelatin, water, oil, and eggs in a large bowl. Beat with an electric mixer on medium speed until well blended, about 2 minutes. Pour batter evenly into 3 (8-inch) round cake pans. Bake in preheated oven until a wooden pick inserted in center comes out clean, about 15 minutes. Cool cake layers in pans 15 minutes; transfer cake layers from pans to a cooling rack. Cool completely, about 45 minutes.
Meanwhile, prepare the Tequila Syrup: Combine sugar and water in a small saucepan. Bring to a boil over high, whisking constantly until sugar is dissolved. Remove from heat. Cool completely, about 20 minutes. Stir in tequila.
Prepare the Icing: Place butter and cream cheese in the bowl of an electric stand mixer, and beat on medium speed until smooth and fluffy, about 2 minutes. Slowly add powdered sugar, and beat on low speed until fully incorporated. Add margarita mixer, lime juice, kosher salt, and 3 drops of the food coloring. Beat until icing is smooth and fluffy and food coloring is fully incorporated.
Reserve 1/4 cup Icing. Assemble cake, 1 layer at a time, brushing each layer with Tequila Syrup before adding Icing. Spread Icing between layers and on top and sides of cake. Stir remaining 2 drops of food coloring into reserved Icing, and spread on sides cake into a unique design. Spread lime curd on top of cake, leaving a 1-inch border. Garnish with lime wedges, sea salt, sparkling sugar, and a straw. Cheers!