Preheat the broiler with a broiler rack about 4 inches from the heat source.

Optionally, cover the broiler pan with foil for easier cleanup.

Arrange red onion, bell pepper, eggplant, and tomato in a broiler pan and broil until softened.

Remove from the broiler, season with salt, and drizzle with olive oil.

Let cool slightly, then coarsely chop the tomato and eggplant.

Reserve.

Heat 6 tablespoons of olive oil in a medium skillet over low heat.

Add the white onion, minced garlic, and bay leaf.

Cook, stirring and pressing the garlic with a wooden spoon to release its flavor, until the onion softens.

Stir in all the remaining ingredients except the tuna and bring to a boil.

Lower the heat and simmer for about 30 minutes.

Let the mixture cool.

Add the tuna to the cooled pickling mixture, spooning some sauce over the top.

Cover and simmer over low heat for about 10 minutes, turning once, until the tuna is cooked through.

Let it cool, then marinate in the refrigerator for 24 hours.

Place the grilled vegetables on a serving platter.

Discard the bay leaf, cut the tuna into chunks, and arrange them over the vegetables.

Serve hot and enjoy this refreshing and flavorful tapa!