Preheat your George Foreman Grill for 5 minutes with the lid closed. Meanwhile, brush each pineapple ring with butter and sprinkle with cinnamon. Place on grill and cook for 2 to 3 minutes per side or until golden.
Sandwich a pineapple ring between donut halves to make a sandwich. Place each on a plate and drizzle with dulce de leche.
Tip: Serve with blueberries and raspberries, if desired.