Perfect for Grilling Bulgur Veggie Burgers with Lime Soy Mayo

(adapted from Epicurious.com) Makes 8-10 patties • 1/2 cup chopped onion, divided • 1 tablespoon olive oil plus additional for brushing • 1/2 cup bulgur • 1 cup water • 1 can black beans, rinsed and drained • ¼ cup Panko breadcrumbs, plus more to achieve desired consistency • 1 1/2 tablespoon soy sauce •…