Prepare the Marinade: In a bowl, combine olive oil, lime juice, minced garlic, cumin, chili powder, paprika, cayenne pepper, salt, and pepper.
Marinate the Chicken: Slice the chicken breasts into thin strips. Add them to the marinade, coating the chicken evenly. Marinate for 30 minutes to 4 hours.
Cook the Chicken: Heat a skillet over medium-high heat. Add the marinated chicken and cook for 6–7 minutes per side, until golden and cooked through. Alternatively, grill the chicken for 5-6 minutes per side. Remove and set aside to rest.
Cook the Vegetables: In the same skillet, add a little more oil if needed. Sauté sliced onions and bell peppers for 5–7 minutes, until tender and slightly caramelized. Stir occasionally.
Warm the Tortillas: Warm the tortillas in a dry skillet or microwave them for 20-30 seconds wrapped in a damp towel.
Assemble the Fajitas: Slice the cooked chicken. To serve, fill each tortilla with chicken, sautéed vegetables, and desired toppings.
