BULGUR VEGGIE BURGERS WITH LIME MAYONAISE

Steps:

• Equipment: a perforated grill sheet * Accompaniments: lettuce; sliced tomato * Cook half of onion with 1/4 tsp salt in oil in a small heavy saucepan over medium heat, stirring occasionally, until golden, 5 to 7 minutes. Add bulgur and water and cook, covered, over low heat until water is absorbed, 15 to 18 minutes. Transfer to a bowl and stir in beans and soy sauce. * Pulse bulgur mixture, walnuts, garlic, cilantro, cumin, cayenne, a rounded 1/4 tsp salt, 1/2 tsp pepper, and remaining onion in a food processor until finely chopped. * Form rounded 1/2 cups of mixture into 4 (31/2-inch-diameter) patties. Chill at least 10 minutes. * While patties chill, stir together mayonnaise, zest, and juice. * Prepare grill for direct-heat cooking over medium-hot charcoal (medium heat for gas); see "Grilling Procedure." Put perforated grill sheet on grill and preheat 10 minutes. * Brush patties all over with oil. * Oil grill sheet, then grill burgers on grill sheet, covered only if using a gas grill, carefully turning once, until golden brown, about 8 minutes total. * Serve burgers open-faced on toast with lime mayonnaise. Cooks' notes: * Burgers can be cooked on the stove. Heat 1 Tbsp oil in a 12-inch heavy skillet over medium heat until it shimmers, then cook patties, carefully turning once, until golden brown, about 8 minutes total. * Uncooked patties can be chilled, covered, up to 4 hours.