Preheat grill to medium-high heat.
In a mixing bowl, combine olive oil, chili powder, cumin, garlic powder, paprika, and lime juice. Mix well.
Add chicken breasts to the bowl and coat them evenly with the marinade. Let it sit for 10 minutes.
Grill chicken for about 6-7 minutes on each side or until fully cooked. Remove from grill and let it rest.
Grill bell peppers and onions for about 5 minutes until they are slightly charred.
Slice the grilled chicken into strips.
In a large bowl, combine romaine lettuce, cherry tomatoes, cilantro, grilled bell peppers, and onions. Top with grilled chicken strips.
Serve immediately and enjoy!