Heat olive oil in saute pan and lightly saute whole garlic cloves for a minute or so. Add harissa, paprika, and cumin, stir well. Add diced tomatoes, tomato paste and water. Mix everything together. Add whole chili, sugar, salt and pepper to taste.

Bring to a boil and cook gently uncovered until the sauce has reduced by half. Stir from time to time to prevent the tomatoes from burning and the mixture from splattering. Simmer for about 30 minutes.

Place fish cutlets in the sauce, cover the saute pan (or transfer into a tray) tightly and put the whole thing in the oven at 180°C (350°F) for the first 10 minutes. Reduce the heat to 150°C (280°F) and let cook for another half hour.

Open the lid to check the consistency and taste of the sauce. Add more salt if needed and some sugar if it is too sour for your palate. If too runny, let it cook uncovered at 180°C in the oven for 10-15 minutes longer.

When ready, remove the fish from the oven and let cool for 15 minutes.

Serve fish on a plate with the sauce spooned over it including the whole garlic cloves. Garnish with fresh cilantro leaves (whole or finely chopped).