Begin by preparing the chicken. Pat the chicken breasts dry with a paper towel and place them in a mixing bowl. Drizzle with olive oil and season with paprika, garlic powder, cumin, salt, and pepper. Toss until the chicken is evenly coated.
Heat a grill pan or skillet over medium-high heat. Once hot, add the seasoned chicken breasts. Cook for about 6-7 minutes on each side, or until fully cooked and the internal temperature reaches 165°F (75°C). Remove from heat and let rest for a few minutes before slicing.
While the chicken is resting, prepare the vegetables. Chop the lettuce, cucumber, tomatoes, and red onion.
Slice the cooked chicken into thin strips.
Warm the pita bread slightly in the grill pan or microwave for about 20 seconds, just until pliable.
Assemble the pitas: Open each pita and stuff it with a portion of the sliced chicken, followed by lettuce, cucumber, tomatoes, red onion, and a generous drizzle of tzatziki sauce.
Serve immediately, enjoying the fresh and flavorful combination.