Step 1

Preheat oven to 400 degrees F. Set a wire rack on a rimmed baking sheet and set aside.

Step 2

With a spoon, gently scoop out the gills that are inside the portobello mushrooms. Discard the gills and set the mushrooms aside.

Step 3

In a medium bowl, add the ricotta cheese, egg, drained spinach, 1 cup of mozzarella cheese, ½ cup of the Parmesan cheese, lemon zest, basil, garlic powder, red pepper flakes, and pinch of nutmeg. Stir until well combined.

Step 4

Divide the ricotta spinach filling between the Portobello mushrooms. Top each mushroom with ¼ cup marinara sauce and the additional mozzarella and Parmesan cheese. Season with salt and pepper, to taste.

Step 5

Place the mushrooms on the wire rack and bake for 20-25 minutes or until the cheese is melted and mushrooms are tender. If you want to brown the cheese on the top, put the pan under the broiler for 1 minute. Make sure you watch the mushrooms closely, the cheese will brown quickly.

Step 6

Remove from oven and garnish with basil. Serve warm.