In a bowl, season the chicken with 2 tablespoons of olive oil, lemon juice, garlic, and spices; set aside.
Add 2 tablespoons of olive oil, onions, and pepper to a skillet on medium high heat. Stir occasionally until onions and peppers are softened, about 4 minutes. Transfer to a bowl and set aside.
Place the chicken slices on the grill cook for about 4 minutes on each side. Place the onion and peppers on the grill with the chicken to warm back through.
As the peppers and onions are warming back up in the grill, warm the tortillas in the microwave for 15 seconds.
To assemble: Place two warm tortillas on a plate and top with chicken, onion, and pepper mixture. You can add salsa, sour cream, cilantro, and Cheddar cheese to top.