Season the tilefish on both sides with salt and pepper. In a large saute pan over high heat, brown the fish on both sides in vegetable oil and then remove the fish from pan. In the same pan, saute the onions until they start to caramelize, then add scallions, tomatoes, garlic, Scotch Bonnet pepper and thyme. Saute for 4 to 6 minutes then add soy sauce and ketchup and stir to combine. Layer fish over onion mixture and then add just enough water to come half way up fish steaks. Season with salt and pepper to taste. Cover pan and simmer for 6 to 10 minutes or until fish is cooked through. Spoon sauce over fish.