Steps
1. In a bowl, combine olive oil, lemon juice, minced garlic, oregano, salt, and pepper.
2. Cut the chicken breast into 1-inch cubes and add to the marinade. Let it marinate for at least 30 minutes.
3. While the chicken marinates, prepare the tzatziki by mixing diced cucumber, Greek yogurt, dill, and lemon juice in a small bowl. Season with salt.
4. Preheat a grill or grill pan over medium-high heat.
5. Thread the marinated chicken onto skewers.
6. Grill the skewers for about 10-12 minutes, turning occasionally, until the chicken is cooked through and golden brown.
7. Warm the pita bread on the grill for a minute.
8. Serve the chicken souvlaki in the pita, topped with tzatziki, cherry tomatoes, and red onion.