balsamic reduction

Tuna steaks are a really versatile cut of fish. They are thick and generous yet light, virtuous, and satisfying. These lemon herb tuna steaks with balsamic vegetables are delectably herby and aromatic, accompanied by a lemony tang, and a hint of sweetness from the balsamic reduction. As the balsamic vinegar cooks and transforms into the reduction, the sugars emerge, leaving behind a sweet and syrupy glaze. The blistered peppers and onions then absorb all of this flavor.

I cook this dish on a grill pan, but you can use a real grill or a cast iron skillet if you don’t have a grill pan. Though I would highly recommend investing in one, as it is fairly inexpensive and can be used endlessly.  

Lemon herb tuna steaks with balsamic vegetables are simple and healthy. Give this dish a try to add some necessary color + brightness to your day during these final days of winter.

serves 4


for the vegetables

  • 2 cups mini sweet bell peppers
  • 1 green bell pepper, sliced in 1-2 inch strips
  • 1 red onion, sliced into ½-inch rings
  • 1 cup balsamic vinegar, divided
  • 1 tablespoon olive oil
  • 1 teaspoon crushed red pepper
  • 1 teaspoon salt
  • ½ teaspoon freshly ground black pepper

for the tuna

  • 4 6-ounce tuna steaks
  • ¼ cup freshly squeezed lemon juice
  • ½ cup parsley, chopped
  • ¼ cup thyme, chopped
  • 1 tablespoon basil, chopped
  • 1 garlic clove, minced
  • 1 teaspoon olive oil
  • ½ teaspoon salt
  • ½ teaspoon freshly ground black pepper


Marinate the peppers and onion in ½ cup of the balsamic vinegar, the olive oil, crushed red pepper, salt, and black pepper. Set aside.

Meanwhile, make the marinade for the tuna by combining the lemon juice, parsley, thyme, basil, garlic, olive oil, salt, and pepper. Coat both sides of the tuna with the marinade and let sit for 20-30 minutes. 

Place the remaining ½ cup of balsamic vinegar in a small pan over medium-low heat until it begins to thicken. This is known as a balsamic reduction, or balsamic drizzle, and it will dress the vegetables once they are cooked. I like to drain the marinade from the peppers, add it to the reduction, and continue reducing it so as not to waste anything!

Heat a grill pan or grill on high heat. Place the peppers and onions on the pan and grill for 6-7 minutes on the first side then turn them using tongs and cook for 6-7 minutes on the other side. Repeat until all of the vegetables have been cooked. 

Once all of the vegetables have been cooked, move the vegetables to a plate and drizzle the balsamic reduction over them. Place the tuna steaks on the grill and cook for 3 minutes on the first side then flip and cook for another 3 minutes. The tuna cooks fairly quickly, so pay attention so as not to overcook in (unless you prefer it that way).

Serve the tuna alongside the vegetables. Feel free to drizzle some of the balsamic reduction over the tuna as well!