Lake Isle Press

Seared Tuna with Sweet-Sour Onions

With red onion crowning each tuna steak, this dish looks pretty and makes an especially nice warm-weather dish, served at room temperature—like most sweet-sour dishes, the taste improves once the tuna and onions have had a chance to spend time together.

Seared Tuna with Sweet-Sour Onions


  • 1 large tuna steak at least 1 inch thick (about 1 pound), cut into 3 or 4 portions
  • Sea salt or kosher salt
  • Freshly ground black pepper (optional)
  • 5 tablespoons red wine vinegar
  • 1 tablespoon sugar, or to taste
  • 1 large red onion, cut pole to pole into thin wedges
  • Extra-virgin olive oil
  • Several mint leaves, snipped into ribbons


1. Season the tuna on both sides with salt and, if using, pepper. In a small bowl, mix the vinegar, sugar, and a pinch of salt with 1/4 cup water.

2. In a heavy-bottomed skillet (such as cast iron), combine the onion with a little olive oil. Cook over medium-low heat, covered, until soft, about 10 minutes. Add the sweet-sour mixture, stirring often as the liquid evaporates and the onions begin to caramelize. Transfer to a bowl.

3. Clean the skillet, add 1 tablespoon olive oil, and raise the heat to medium. Sear the tuna until well browned. Turn the steaks and pile the onions on top. As soon as the second side is browned, reduce the heat and add a little water. Simmer a minute or so more for medium rare, and a little longer for medium.

4. Transfer the tuna to dinner plates. Deglaze the pan by adding a little water and cook until thickened; drizzle over the onion-topped tuna steaks. Sprinkle with the mint. Serve warm or at room temperature.

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