In a mixing bowl, combine olive oil, lime juice, cumin, paprika, garlic powder, salt, and black pepper. Add the chicken breasts and coat well. Marinate for at least 15 minutes.

Preheat the grill to medium-high heat. Remove the chicken from the marinade and grill for about 6-7 minutes on each side, or until fully cooked and internal temperature reaches 165°F (75°C).

Once cooked, let the chicken rest for a few minutes before slicing it into strips. Warm the corn tortillas on the grill for about 30 seconds on each side.

Assemble the tacos by placing sliced chicken on each tortilla and topping with lettuce, tomatoes, cheese, sour cream, cilantro, and jalapeños as desired.