Mix beef, onions, crumbs, mint, salt and pepper; add water, small amount at a time, just until mixture holds together. Form into bite-sized balls; arrange balls in single layer in shallow oven dish. Pour tomatoes over meatballs; sprinkle with cinnamon. Dot with butter. Bake in 400-degree oven for 1 hour. Serve with toothpicks. Yield: 50 meatballs.