In the same skillet, brown the onion. Add oil, if needed. Add the pineapple and red bell pepper and cook for about 2 minutes. Season with salt and pepper. Add the sauce and bring to a boil, stirring constantly. Return the meatballs to the skillet. Cover and simmer for about 5 minutes or until the meatballs are cooked. Serve with rice and garnish with cilantro.