Brown hamburger, (You can add onions, peppers & mushrooms, or not). What ever you like. Add the jar of sauce, and about 1 cup of water.
Spray cooking spray lightly in bottom of 7x11" baking dish.
Layer a small amount of sauce, then ravioli's, cheese layer and repeat. I usually keep a small amount of cheese for the top.
Bake 35 to 45 minutes, or until the lasagna is lightly browned and bubbly.