Polynesian Burgers

Name: Polynesian Burgers
Ingredients: 3 limes; 1/4 cup sugar, plus more to taste if needed; 1 tablespoon cornstarch; 2 pounds ground beef; Kosher salt and freshly ground black pepper; 1 gold pineapple, or regular pineapple if gold is unavailable, peeled, cored and cut into 1/4-inch-thick rings; 1 red bell pepper, seeded and cut into 1/2-inch-thick rings; 1 orange bell pepper, seeded and cut into 1/2-inch-thick rings; 1 yellow bell pepper, seeded and cut into 1/2-inch-thick rings; 1 large sweet red onion, cut into 1/2-inch-thick rings; 6 hamburger buns; 1 large star fruit, sliced; 3 blood oranges or regular oranges; 3 lemons