This vegan twist on an Asian takeout favorite lets mushrooms do the heavy lifting for a hearty texture and dose of antioxidants with bell peppers and fresh pineapple!
Stir together ingredients for the sauce in a small mixing bowl until tomato paste is completely incorporated. Set aside.
Heat olive oil over medium heat in a medium cast-iron skillet. Add mushrooms, bell pepper, and onion and sauté for 10 minutes, stirring occasionally. Pour in the sauce and reduce heat to medium-low. Stir in pineapple. Continue to cook uncovered for 8-10 minutes longer.
Serve sweet and sour mushrooms over rice garnished with green onion and sesame seeds