Gut, scale, and remove the heads from the red mullets. Fillet the fish and carefully remove the bones. Clean the squid, extracting the ink sacs from their pockets. Keep all ingredients chilled.
Halve the green pepper, remove the stem, and slice thinly. Peel and chop the garlic cloves. Sauté the garlic and pepper over low heat until browned, cover, and simmer. Add peeled, seeded, and chopped tomatoes, thinly sliced onions, and fish stock. Simmer until everything is fully cooked.
Blend the sauce smooth, stir in the squid ink, adjust seasoning, and strain through cheesecloth for a silky texture.
Season the red mullet fillets and squid with salt and pepper. Sear in a very hot pan with olive oil.
To serve, spoon ink sauce onto each plate and top with the seared red mullet fillets and squid.
