Cut the tomato in half horizontally, remove seeds, and dice into 7mm cubes. Dice the zucchini and basil leaves into 7mm cubes as well.

Pat the horse mackerel fillets dry with kitchen paper, season with salt and pepper, and coat with plain flour.

Heat butter in a frying pan over medium heat. Place the horse mackerel skin-side down and cook until golden brown. Flip and cook for another 2 minutes until fully cooked.

In a bowl, mix the diced tomato, zucchini, basil, and the basil tomato sauce ingredients (salt, olive oil, pepper).