Beef Burgers with Caramelized Onions

Combine bulgur with 1/2 cup warm water in a small bowl; let stand until the water is absorbed and the bulgur is tender, about 30 minutes.

Meanwhile, heat oil in a large nonstick skillet over low heat. Add onions and sugar; sauté until the onions are very tender and golden, about 15 minutes. Stir in 1/4 cup water and vinegar. Season with salt and keep warm.

Preheat grill or broiler.

Combine the plumped bulgur, beef, tomato paste, parsley, salt and pepper in a medium bowl; mix thoroughly but lightly. Shape into four 3/4-inch-thick patties. Grill or broil on a lightly oiled rack until browned and cooked through, about 5 minutes per side. Place the patties on buns, top with the caramelized onions and garnish with lettuce.