01 - Preheat oven to 350°F. In a bowl, mix graham cracker crumbs, melted butter, and sugar until the mixture resembles wet sand. Press the mixture evenly into the bottoms and sides of 6 mini tart pans. Bake for 8-10 minutes. Let cool completely.
02 - In a blender, purée watermelon, lime juice, and honey until smooth. Strain to remove any pulp.
03 - In a separate bowl, beat cream cheese until smooth. Add sweetened condensed milk, heavy cream, lemon zest, and lemon juice. Beat until light and creamy.
04 - Pour the lemon cream into the cooled tart shells, spreading evenly. Spoon a thin layer of the watermelon purée over the lemon cream and lightly swirl with a skewer for a marbled effect.
05 - Freeze tarts for at least 3 hours or until set. To serve, let sit at room temperature for 10 minutes to slightly soften. Garnish with mint, watermelon balls, and extra lemon zest.