Chicken Pita With Tzatziki Recipe

Name: Chicken Pita With Tzatziki Recipe
Ingredients: 2 tablespoons olive oil; 1 1/2 pounds boneless, skinless chicken thighs (about 8); 1/4 teaspoon cayenne pepper; kosher salt and black pepper; 1 cup low-fat Greek yogurt; 1 cucumber, seeded and grated (about 1 1?4 cups); 1/4 cup chopped fresh mint; 1/2 small clove garlic, finely chopped; 4 flat breads or pocketless pitas, warmed; 1 small romaine heart, leaves torn if large; 8 cherry tomatoes, quartered