Sultry Cheesy Caramelized Onion Portobello Mushrooms

1. Preheat oven to 400°F (200°C). Bake mushroom caps, gills up, for about 15 minutes.
2. Meanwhile, caramelize your onions: Fry 1 large red onion in 2 tablespoons of olive, avocado, or coconut oil.
3. Add 1-2 tablespoons of balsamic vinegar and 1 tablespoon of brown or coconut sugar to the onions. Season with a pinch of salt and pepper (optional).
4. Once mushrooms are baked, take them out of the oven and blot with a towel to remove excess moisture.
5. Fill the mushroom caps with the caramelized onions.
6. Top each filled mushroom cap with a slice of provolone or your cheese of choice.
7. Broil for 2 minutes or until the cheese is melted and bubbly.