The key to perfect Poisson Braisé is an intense marinade that must penetrate deep into the fish. Make sure to score the fish thoroughly to allow the marinade to reach the deepest parts. Grilling over charcoal is ideal, but you can also use an oven or a pan. The fish should be crispy on the outside and tender and juicy on the inside. It is usually served whole, which adds to its authenticity.
Wash and pat the fish dry. Make three to four deep diagonal cuts on each side. Drizzle with lemon juice and lightly sprinkle with salt.
In a blender or mortar, blend all the marinade ingredients (onion, garlic, ginger, pepper, tomato paste, oil, paprika, salt, and pepper) into a thick paste.
Rub the marinade thoroughly onto the fish, both outside and inside the cuts and belly cavity. Marinate at room temperature for a minimum of 30 minutes, or in the refrigerator for up to 2 hours.
Preheat the grill to medium-high heat (or the oven to 185 °C (365 °F)). Lightly grease the grill rack to prevent sticking.
Grill the fish for 10 to 15 minutes per side, depending on its thickness. The fish is done when the skin is crispy and the meat flakes easily with a fork (internal temperature 63 °C (145 °F)).
Serve Poisson Braisé hot, drizzled with any remaining oil or grilling juices. It is traditionally served with Atassi (rice and beans) or french fries, plus sliced fresh onion, tomato, and an extra portion of spicy sauce.