Lamb Burgers with Fennel Salad

1/2 cup fat-free sour cream

1/2 cup plain fat-free yogurt

1/4 cup finely chopped red onion

2 tablespoons chopped fresh mint

1 tablespoon grated lemon rind

1 tablespoon honey

1/4 teaspoon black pepper

1 garlic clove, minced

1/2 cup (2 ounces) crumbled feta cheese with basil and garlic

1/4 cup chopped pimiento-stuffed olives

2 tablespoons Greek seasoning (such as McCormick)

1/4 teaspoon salt

1 pound lean ground lamb

1 pound ground turkey breast

Cooking spray

4 (6-inch) pitas, cut in half