Finely chop the onion and garlic. Chop the tomatoes into small cubes. Drain and rinse the beans, drain again.
Heat half of the oil in a frying pan, add the onion and cook for 5 minutes. Add the garlic, then after 1 minute, the chopped tomato pieces and the thyme leaves. Cook for about 10 minutes over low heat until you get a thick sauce.
Add the sugar and beans, then season with salt & pepper to your liking. Simmer gently.
Meanwhile, wash and dry the fish, then rub with oil and the paprika.
Heat your grill/BBQ or griddle pan and cook for 2-3 minutes on each side, until charred and cooked through. Squeeze lemon juice over the fillets during the cooking.
Season with salt and pepper and serve with the bean sauce.