Place the portobello mushroom caps upside down on the cookie sheet and place in the oven. Turn the oven on to 425 degrees and let the mushrooms cook while the oven comes to temp.
2 large portobello mushroom caps
While the mushrooms are cooking, combine the quinoa, spinach, tomatoes, vinegar, garlic powder and salt.
½ cup cooked quinoa, About a cup and half of fresh spinach, Handful of grape tomatoes, 1 teaspoon balsamic vinegar, ¼ teaspoon garlic powder, Pinch of kosher salt
Once the oven reaches 425, remove the mushroom caps, which will now be partially cooked. Flip over the caps, pile on the quinoa mixture and top with a half an ounce of cheese each.
1 ounce sliced parmesan cheese
Return to the oven and bake for an additional 6-8 minutes until the cheese melts.