Preheat the oven to 425 degrees. **
In a skillet over medium heat saute the onion and bell pepper in the olive oil until soft. Add the black beans, quinoa, spice blend and salt and pepper to taste.
Carefully remove the stems and wipe the mushroom caps clean. Scoop out the gills with a spoon. Place the mushrooms on a foil covered baking sheet or baking dish.
Stuff the mushrooms with the black bean mixture. Top with the cheese.
Bake for 10-15 minutes until the cheese is melted.
Top with the guacamole, green onions, and cilantro.