2 1/2 cups graham cracker crumbs
1 cup sugar, divided
1 1/2 sticks butter, melted
5 cups watermelon juice, divided
1/2 cup lemon juice
1/3 cup milk
1/2 teaspoon lemon zest
1 (1-ounce) package unflavored gelatin
Directions1.In a medium bowl, combine graham cracker crumbs, 1/2 cup sugar, and the butter; mix well. Press crumb mixture evenly into a 9- x 13-inch baking dish and refrigerate.
2.In a large bowl, combine 3 cups watermelon juice, the lemon juice, milk, remaining 1/2 cup sugar, and lemon zest; mix well until sugar dissolves, then set aside.
3.Place remaining 2 cups watermelon juice in a medium microwave-safe bowl and sprinkle gelatin over juice. Let sit 2 minutes, or until gelatin is absorbed. Microwave 1-1/2 minutes, or until liquid is smooth after stirring. Stir gelatin mixture into watermelon mixture. Slowly pour over prepared crust.
4.Place in freezer 1-1/2 hours, or until mixture is set. Remove from freezer and place in refrigerator 4 hours, or until firm. Cut into squares. Store leftovers in refrigerator.