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. Sauté 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.