• 4 boneless and skinless chicken breast halves
• 8 corn tortillas (6 inches each)

For the Seasoning

• 1/4 cup freshly squeezed lime juice
• 1/4 cup extra-virgin olive oil, plus more for brushing
• 1 teaspoon coarse salt, plus more for seasoning
• 1/4 teaspoon freshly ground pepper, plus more for seasoning
• 2 red onions, sliced into 1/2-inch-thick rounds

For the Topping

• Chopped lettuce, sliced tomatoes and avocados, fresh cilantro, and sour cream, for serving