In a skillet, cook onion and garlic in hot oil until tender but not brown; remove. Brown chicken, then return onion and garlic to pan. Add tomato liquid, lime juice, salt, oregano and pepper. Simmer, covered, 30 minutes. Cut up tomatoes if whole and add to pan with raisins and lime zest. Simmer, covered, about 25 minutes, until chicken is cooked through. Remove chicken, skim fat from sauce, and stir in pineapple, rum and flour mixture. Cook, stirring, until thickened. Return chicken to sauce and warm through. Serve over rice.