Preparation Combine lamb, 1/2 cup onions, 1 teaspoon salt, pumpkin pie spice, and 1/4 teaspoon cayenne pepper in medium bowl. Mix gently. Using moistened hands, form lamb mixture into 4 equal patties, each about 1/2 inch thick. Combine yogurt, cumin, remaining 1/2 cup onions, 1/4 teaspoon salt, and 1/4 teaspoon cayenne pepper in small bowl. Stir to blend. Let stand 15 minutes. Prepare barbecue (medium-high heat). Grill burgers until cooked to desired doneness, about 4 minutes per side for medium. Carefully open pita breads to make pockets; insert burger in each. Spoon in yogurt mixture and tomatoes, dividing equally, and serve.
Preparation Combine lamb, 1/2 cup onions, 1 teaspoon salt, pumpkin pie spice, and 1/4 teaspoon cayenne pepper in medium bowl. Mix gently. Using moistened hands, form lamb mixture into 4 equal patties, each about 1/2 inch thick. Combine yogurt, cumin, remaining 1/2 cup onions, 1/4 teaspoon salt, and 1/4 teaspoon cayenne pepper in small bowl. Stir to blend. Let stand 15 minutes. Prepare barbecue (medium-high heat). Grill burgers until cooked to desired doneness, about 4 minutes per side for medium. Carefully open pita breads to make pockets; insert burger in each. Spoon in yogurt mixture and tomatoes, dividing equally, and serve.