Ingredients

• 4 large portobello mushroom caps
• 0.5 cups soy sauce
• 0.5 cups balsamic vinegar
• 4 cloves garlic , chopped, or more to taste
• 1 large red bell pepper
• 1 cup reduced-fat mayonnaise
• 1 tablespoon cayenne pepper , or to taste
• 4 hamburgers buns , split

Instructions

1. 1 Place mushrooms into a large resealable plastic bag; add soy sauce, balsamic vinegar, and garlic. Seal bag and shake to combine ingredients; marinate mushrooms at room temperature for 2 to 3 hours, turning bag occasionally.
2. 2 Preheat grill for medium-high heat and lightly oil the grate.
3. 3 Place red bell pepper onto the grate and grill until the skin is blistered and charred, turning often, about 10 minutes. Transfer pepper to a bowl and cover with plastic wrap; let pepper cool. When pepper is cool enough to handle, remove and discard skin, stem and seed the pepper, and chop.
4. 4 Mix pepper into mayonnaise in a bowl and stir in cayenne pepper. Chill red pepper mayonnaise until serving time.
5. 5 Grill marinated mushroom caps until browned and juicy, about 6 minutes per side. Serve mushrooms on buns, topped with red pepper mayonnaise.

Nutrition per serving