Tuna Marinated with Onions and Capers

Tonno Marinato

Preparation info

  • Difficulty


  • Serves


    as a main course

Appears in

One time I found myself with quite a bit of leftover grilled tuna. I didn’t want to reheat it since it would inevitably overcook. Recalling that Venetians marinate fried sole in sweet-and-sour onions, and leftover boiled beef is often served with smothered onions, I decided to marinate the tuna with caramelized onions and capers and serve it the next day. It was so good that now I grill tuna expressly to marinate it this way.

Preparation time: 25 minutes
Total time from start to finish: 12½ or more hours


  • 2 medium sweet yellow onions
  • 5 tablespoons extra virgin olive oil
  • Salt
  • Freshly ground black pepper
  • pounds fresh tuna steaks, about ¾ inch thick
  • 2 tablespoons capers


  1. Preheat a charcoal or gas grill.
  2. Peel, halve, and thinly slice the onions crosswise. Put them in a skillet with 4 tablespoons of the olive oil. Place over medium-high heat and season with salt and pepper. When the onions begin to brown, reduce the heat to low and cook, stirring occasionally, until the onions become very soft, 15 to 20 minutes.
  3. While the onions are cooking, drizzle both sides of the tuna steaks with the remaining 1 tablespoon olive oil and season with salt and pepper. Grill for 2 to 3 minutes on each side for medium-rare tuna. Remove from the grill and place in a deep platter.
  4. When the onions are done, add the capers and cook for another minute. Pour the contents of the pan over the tuna. When it is cool, cover with plastic wrap and refrigerate for at least 12 hours. Serve at room temperature.