Wash fish fillets and pat dry. Rub them with one teaspoon salt and one teaspoon curry.
Place the fish on a grill-safe pan or tray that's been covered with foil. Cover, to keep the fish from drying out and refrigerate until ready to cook.
Sauce: Chop half of the onion, along with the cloves of garlic, and sauté in vegetable oil until translucent.
Chop one of the tomatoes and add to the same pan, along with the parsley, tomato paste, vinegar, lemon juice, water, remaining salt, and curry.
Add cayenne pepper, if using. Stir until all the ingredients come together to form a nice, rich sauce. Simmer for approximately five minutes and set aside to cool.
Slice the remaining onion and tomato. Remove the fish from the refrigerator and smother with the tomato sauce.
Arrange the sliced tomatoes and onions on top of the sauce. I grilled the fish in a grill basket to achieve that classic smokey masgouf flavor, but you can also bake it in the oven.
Heat your barbecue grill, and once hot, add the fish. Cook for approximately 10 minutes. Flip halfway through.
Served with white rice, topped with the tangy tomato sauce.