Cut a thick 3-inch slice from the center of the melon (to look like a big cake layer). Trim the rind from the slice. Place on a platter. Remove strawberry greens, then thinly slice the fruit. Overlap slices around the base of the watermelon. Whip the cream and sugar to stiff peaks. Spoon cream on top and sprinkle with raspberries and pistachios.
Cut a 2½- to 3-inch-thick slice from the center of the melon. Discard seeds and trim rind, making the edges straight. Place piece on a platter. Peel kiwi, slice in half lengthwise and slice into thin half-moons. Layer kiwi along the bottom edge of the melon. Whip the cream and sugar to stiff peaks. Fill center of the melon with extra fruit and cream. Spread a thin layer of cream on the top. Slice grapes in half lengthwise and decorate the top in concentric circles.
If using a large melon, cut a 2½-inch slice from the center and use one of the ends for the smaller top piece. If using 2 small melons, cut thick slices from each melon for the cake. Discard seeds and trim rind, making the edges straight. Stack pieces on a platter. Peel mango and cut one side off the pit. Cut mango cheek into very thin slices and bend in half, layering them along the bottom edge of the cantaloupe. Whip cream and sugar to stiff peaks. Fill the center of the cantaloupe with extra diced fruit and cream. Pile blueberries on top and sprinkle with coconut.
•• The NUTRITION FACTS here are for one serving of EACH cake. Divide by three to get the nutrition for one serving of one cake, roughly.
• These "cakes" are actually made from pretty summer fruit. Just slice and serve.