For the Chicken
Mix onion, bell pepper, lime juice, thyme, garlic cloves, and chicken breasts in a bowl. Cover and refrigerate for one hour, turning occasionally.
Remove chicken from marinade, reserving marinade. Sprinkle chicken with salt and pepper. Cook in a large non-stick skillet coated with cooking spray over medium high heat; saute until browned. Add reserved marinade, salt (to taste), tomatoes, water, and serrano pepper; bring to a boil. Cover, reduce heat, and simmer 45 minutes. Discard chile. Top each chicken breast half with tomato mixture; serve with tropical salsa, plantains, and rice.
For the Tropical Salsa
Mix sugar, rum, and lime juice in a large bowl,. Add serrano pepper, pineapple chunks, mango, and carambola; toss to coat. Chill at least 2 hours.
For the Sauteed Plantains
Cook plantains in a large nonstick skillet over medium high heat. Saute until browned.