Stuffed Portabella Mushroom Burger - Oryana

Ingredients

• 4 tablespoons olive oil, divided
• 1 medium red onion, chopped
• 1 medium red pepper, seeded and chopped
• 2 cups, packed baby spinach
• 3 cloves garlic, minced
• 2 tablespoons coconut aminos (or tamari)
• 1 tablespoon balsamic vinegar
• 4 large portabella mushrooms
• Salt and pepper to taste