Devilled fish is a must-try Sri Lankan - Chinese fusion dish that is very popular and one of my favorite dishes of all time! It might look like a complicated recipe but trust me it's very easy. Just follow the steps.
Cut tuna into large chunks (about 2 inches long cuboids)
Make the marinate with paprika or chili powder, black pepper, lime salt, and water. Add the fish pieces and mix to coat every piece with the marinade*. Be careful to do it gently as the fish pieces can break apart. Set it aside and let it marinate until you make the sauce and get the other ingredients ready. (about 10 - 15 mins)
Heat enough oil to deep fry into a deep skillet. Wait until the oil is hot. Gently add fish pieces to the oil, and fry them until the edges start to turn golden and the fish is all the way cooked through*. Transfer fish to a paper towel-lined plate.
Add cornstarch and water to a small bowl. mix. And then add all the rest of the sauce ingredients which are ketchup, chili sauce, soy sauce, sugar, and salt. Mix and keep it aside.
Crush ginger and garlic in a mortar and pestle or chop them very finely.
Cut banana peppers into rounds. Cut onion into large triangular pieces or rounds, and tomato into wedges.
Heat a medium size wok or a saute pan. Add oil and let the oil heat up. Add cinnamon stick, ginger, garlic, curry leaves, and pandan leaves. Saute until the garlic starts to turn golden on the edges.
Add chili flakes, chili paste*, and black pepper. Saute for about 10 seconds or until chili flakes turn dark red.
Add banana peppers and onions. Saute for another 10-15 seconds just mix it through.
Then move everything to a side and add the sauce. Let the sauce heat up. When the sauce is heated up, mix it with the vegetables.
Add fried fish pieces. Gently mix everything well to coat all the fish pieces with the sauce (make sure not to break your fish pieces.) Adjust salt if needed.
Add tomatoes. Mix very lightly. You can serve the dish at this point*. Or proceed to the next step if you like to have more gravy.
Add 1/2 cup of water and mix. Let the gravy heat up and when it starts to turn thick, turn off the heat. It will get thicker as it cools down. Do not simmer too long as it can overcook fish and vegetables.