Frozen Margarita Pie

Butter 9-inch pie plate. Combine the crushed pretzels, sugar and butter in a medium bowl. Mix together well and press into the prepared pie plate. Chill the crust for 1 hour. Combine the lime zest, lime juice, sweetened condensed milk, tequila and triple sec in a medium bowl. Fold in 1 cup of the whipped cream and the food coloring. Pour the mixture into the prepared crust. Cover and freeze for at least 4 hours. Decorate the pie with the remaining whipped cream and whole pretzels. Serve cold.