3/4 pound skinless, boneless chicken breast halves
1/2 cup reduced-fat plain yogurt
2 tablespoons reduced-fat mayonnaise
1 tablespoon Dijon mustard
1/4 teaspoon ground cumin
1/8 teaspoon cayenne pepper
2 cups fresh baby spinach
1/2 cup chopped seeded cucumber
2 green onions, sliced
4 (6-inch) pita breads, halved