According to the website Simplify Supper (where I found this recipe) it's a Weight Watcher's recipe. My kids don't like it as well as regular lasagna but I think it's great and it's SO easy.
28 ounces spaghetti sauce
6 Uncooked Lasagna Noodles
15 ounces Fat-free ricotta cheese
6 ounces fresh baby spinach
8 ounces fresh sliced mushrooms
8 ounces low-fat mozzarella cheese
Preheat oven to 375. Spread 1/3 of the sauce on bottom of l9x13 casserole dish. Arrange 3 noodles in a single layer over sauce. Top with all of the ricotta cheese and vegetables, another 1/3 of sauce, and 1/2 of mozzarella cheese. Then add remaining noodles in a single layer. Spread evenly with remaining sauce. Cover dish with foil; bake until noodles are tender and mixture is piping hot, about 1 hour. Sprinkle with remaining mozzarella cheese; bake uncovered 5 minutes longer. Let stand 5 minutes before serving.