Cut the tomatoes and onions into quarters and place in a baking dish, season and drizzle with 2 tablespoons of olive oil. Bake at 190 degrees for 10-15 minutes.
Season the fish and wrap with bacon slices.
Add tomato paste, sliced olives to the tomatoes and mix well.
Place the fish and pour over the remaining oil. Bake for another 20 minutes.
Sprinkle with chopped basil leaves before serving.