1. Combine ground sirloin, 3 Tbsp. (45mL) Mrs. Dash� Hamburger Grilling Blend, and egg substitute in a medium bowl. Shape meat mixture into eight 4-inch (10cm) round, flat patties.
2. Place a piece of cheese on top of one hamburger patty, top with a second patty and press down firmly, sealing the sides by pinching together.
3. Heat olive oil in a medium skillet and add onion, remaining Mrs. Dash� Hamburger Grilling Blend, and balsamic vinegar. Saut� onions on low heat until soft and browned.
4. Meanwhile place burgers under preheated broiler or grill and brown patties on both sides until juices run clear, about 3 minutes per side. Top burgers with onions and place in bun to serve.