Mix olive oil, lemon juice, garlic powder, onion powder, paprika, salt, and pepper in a bowl, then coat the chicken and marinate 15 to 30 minutes.
Heat a grill pan or skillet over medium-high heat and cook chicken for 5 to 6 minutes per side until the internal temperature reaches 74°C. Add cheese during the last minute if using.
Rest the chicken for 5 minutes, then slice it.
Toast buns and spread with mayonnaise or mustard.
Assemble with lettuce, sliced chicken, tomato, and optional pickles or onion, then serve right away.