Portobello Mushrooms & Onions with Balsamic Glaze

Ingredients (8)

• 1 Pepper to taste Freshly ground
• 0.25 tsp crushed red pepper flakes optional
• 1 Sea salt to taste
• 6 Portobello mushrooms sliced 1/4-inch thick, or 16 ounces of any mushroom
• 2 cup onion(s) thinly sliced
• 2 clove garlic minced
• 2 tsp olive oil
• 0.75 cup balsamic vinegar