Place tortilla on a baking pan that has been sprayed with Pam Olive Oil spray. Saute onions and mushrooms in a pan sprayed with Pam butter spray until tender. Set aside. Wilt spinach in the same pan. Remove from pan and chop. Place sauce onto the tortilla and top with 1/2 cup of the mozzarella cheese. Then place the onion, mushroom and wilted spinach on top of the cheese. Finish off with the remaining mozzarella, feta, and grated cheese. Place in oven set at 375* and bake for 7-10 min. Until cheese is melted and bubbly