Ingredients

• Ingredients
  1. 3 tablespoons olive oil
  2. 2 medium red onions, thinly sliced
  3. Salt
  4. 1 teaspoon chipotle powder or hot paprika
  5. 1 teaspoon dried oregano
  6. 1 tablespoon red wine vinegar
  7. 1 ripe mango—peeled, pitted and cut into 1/4-inch dice
  8. 1 medium cucumber—peeled, seeded and cut into 1/4-inch dice
  9. 1 serrano or jalapeño chile, seeded and very finely chopped
  10. 2 tablespoons fresh lime juice
  11. 1 tablespoon chopped cilantro
  12. One 1-pound tuna steak (1 inch thick)
  13. Eight 6-inch corn tortillas

Directions

1. Light a grill or preheat a grill pan. In a large skillet, heat 2 tablespoons of the olive oil. Add the onions, season with salt and cook over moderately high heat until softened and browned, about 8 minutes. Add the chipotle powder and cook for 30 seconds. Add the oregano and the vinegar and cook for 1 minute. Transfer to a plate.
2. Meanwhile, in a bowl, combine the mango, cucumber, serrano, lime juice and cilantro and season the salsa with salt.
3. Oil the grill. Rub the tuna with the remaining 1 tablespoon of olive oil and season with salt. Grill over high heat until lightly charred and pink within, about 3 minutes per side. Transfer to a plate. Grill the tortillas until hot and soft, about 10 seconds. Stack the tortillas and wrap them in foil to keep warm.
4. Thinly slice the tuna and transfer to a platter. Serve with the onions, salsa and tortillas. Let everyone make their own tacos.