Spray 16 regular-size muffin cups with Crisco® Original No-Stick Cooking Spray. Heat oil in 10-inch skillet over medium heat. Cook onions in oil 15 to 20 minutes or until transparent, stirring occasionally. Set aside.
Heat oven to 350°F. In large bowl, combine turkey, applesauce, 1/4 cup of the maple syrup, egg, onion salt, garlic powder and bread crumbs; mix thoroughly. Fill each muffin cup with about 1/4 cup of meat mixture; press firmly into cup.
Bake 10 minutes. Meanwhile, remove crescent rounds from can; do not unroll. Using serrated knife, cut roll evenly into 16 rounds; carefully separate rounds.
Remove burgers from oven. Evenly divide onions among tops of burgers in cups. Top each with 1 square of cheese and 1 crescent round.
Bake an additional 14 to 20 minutes or until thermometer inserted in center of turkey burgers reads 165°F and crescents are golden brown. Meanwhile, in small bowl, beat together remaining 1/2 cup maple syrup, mayonnaise and mustard with wire whisk until blended.
Remove burgers from oven; let stand 5 minutes. With thin metal spatula, remove each burger from cup and turn upside down onto individual serving plate. Top each with tomato. Serve with maple-mustard sauce.