Makes 4-6 servings. Difficulty
2 Tablespoons olive oil 1 medium red onion, thinly sliced Salt 1/4 teaspoon chipotle powder 2 teaspoons fresh oregano 1 Tablespoon red wine vinegar 1 ripe mango, peeled, seeded and diced 1 medium cucumber, peeled, seeded and diced 1/2 jalapeno pepper, seeded, stemmed and minced 2 roma tomatoes, diced 2 Tablespoons fresh lime juice 1 Tablespoon cilantro, chopped 1 lb. tuna steak 12 corn tortillas
Prepare the grill. In a large skillet, heat 1 tablespoon olive oil over medium high heat. Add the onions. Season with salt and cook, stirring occasionally, until softened and golden, about 8 minutes. Add the chipotle powder and cook for 30 seconds. Add the oregano and red wine vinegar; cook for 1 minute. Transfer to a plate and set aside.
Meanwhile, in a bowl, combine the mango, cucumber, jalapeno pepper, tomatoes, lime juice and cilantro. Adjust seasonings to taste with salt and freshly ground black pepper. Set aside.
Rub the tuna steak all over with the remaining tablespoon of olive oil. Season on both sides with salt and freshly ground black pepper. Grill over high heat until lightly charred and pink on the inside, about 3 minutes per side. Transfer the tuna steak to a plate.
Warm the tortillas in a dry skillet and keep warm wrapped in foil.
Thinly slice the tuna steak and transfer to a platter. Serve the tuna with the onions, mango-cucumber salsa and warm tortillas.