Preheat oven to 350°.
Cover a large baking sheet with parchment paper. Draw 6 (4-inch) circles on paper. Turn paper over; secure with masking tape.
Beat egg whites, cornstarch, and salt at high speed of a mixer until foamy. Add granulated sugar and brown sugar, 1 tablespoon at a time, beating until thick and glossy. Add vanilla, beating well. Divide egg white mixture evenly among the 6 drawn circles. Shape meringues into nests with 1-inch sides using the back of a spoon. Place meringues in oven. Immediately reduce oven temperature to 300°; bake 1 hour. Turn oven off; cool meringues in closed oven at least 4 hours or until completely dry. (Meringues are done when the surface is dry and meringues can be removed from paper without sticking to fingers.) Carefully remove meringue nests from paper.
Beat whipping cream, powdered sugar, and cinnamon at high speed of a mixer until stiff peaks form. Dollop 1/4 cup whipped cream into each meringue nest. Top each with 1/2 cup pineapple, 2 tablespoons kiwi, and 2 tablespoons blackberries. Drizzle 1 1/2 teaspoons caramel syrup over each serving. Serve immediately.
Note: Whipping cream whips better when bowl and beaters are chilled.