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. Add chicken to the same skillet and cook for about 4 minutes on each side. Return the onion and peppers to the skillet and stir for about 2 more minutes.
As the peppers and onions are warming back up in the skillet, 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 and Cheddar cheese to top.