Instructions

For the Crust: Place oven rack in middle position and heat oven to 350 degrees. Grease 9-inch springform pan and line perimeter with 3-inch-wide strip of parchment paper. Process coconut and lime zest in food processor until coarsely ground; reserve ½ cup. Add pretzels to remaining coconut mixture and process until finely ground. Add melted butter and pulse to combine. Press mixture into bottom of prepared pan. Bake until edges are golden, 10 to 12 minutes. Cool completely.
For the Filling: Combine ¼ cup water and gelatin in small saucepan and let sit until gelatin softens, about 5 minutes. Add margarita mix, tequila, and triple sec and cook over low heat, stirring frequently, until gelatin dissolves, about 5 minutes. Cool 15 minutes. Using mixer fitted with whisk, whip cream on medium-low speed until foamy. Increase speed to high and whip until soft peaks form. Using clean bowl, whip sweetened condensed milk and cream cheese until combined. Add 1 cup margarita mixture and whip until incorporated. Fold in one-third whipped cream, then gently fold in remaining whipped cream. Pour filling into crust. Refrigerate until just set, about 1 hour.
For the Topping: Stir remaining ½ cup water into remaining margarita mixture. Pour mixture through fine-mesh strainer into 2-cup liquid measuring cup. Pour over filling and refrigerate until set, about 4 hours. Remove sides of pan and parchment. Press reserved coconut mixture onto sides of cake and top with lime slices. Serve.