Remove any tough stems and slice mushrooms. Heat oil in a large saute pan over high heat. Add mushrooms and cook for about 5 minutes until browned. Fold in spinach, add pinch of salt and cook until spinach is wilted; about 3 minutes. Turn off heat.

Heat oven to 375.

Cook noodles according to the directions. Ladle 1 cup of sauce into bottom of 11x7 pan. Cover bottom with noodles. Spread 1/3 of ricotta, followed by 1/3 mushrooms, then another cup of sauce. Sprinkle a 1/4 of the mozzarella, then layer noodles. Repeat layers ending with noodles the last of the sauce and remaining ricotta. Layer tomatoes then top with remaining mozzarella.

Cover with foil and bake in the oven for 30 minutes. Remove foil and continue to bake 25-30 minutes, or until edges of the noodles brown.

Let sit for 15 minutes before serving.