Pita Sandwiches with Grilled Beef Patties and Lemon-Tahini Sauce

• ⅓ cup bulgur wheat bulgur wheat
• 1 pound lean ground beef lean ground beef
• ½ yellow onion, about 8 ounces, minced or grated on the large holes of a box grater yellow onion, about 8 ounces, minced or grated on the large holes of a box grater
• 2 tablespoons finely chopped fresh Italian parsley leaves finely chopped fresh Italian parsley leaves
• 2 tablespoons chopped fresh chives chopped fresh chives
• 1½ teaspoon chopped fresh thyme leaves chopped fresh thyme leaves
• 1¼ teaspoon kosher salt kosher salt
• 3 garlic cloves, minced or pushed through a press garlic cloves, minced or pushed through a press
• 1 teaspoon ground cumin ground cumin
• ¼ teaspoon crushed red pepper flakes crushed red pepper flakes
• ⅛ teaspoon freshly ground black pepper freshly ground black pepper

Sauce