Cook Noodles According To Package Directions; Drain. Add Butter; Toss To Coat. In A Large Skillet, Cook Beef Over Medium Heat Until No Longer Pink; Drain. Spread A Fourth Of The Spaghetti Sauce Into An Ungreased 5-Qt. Slow Cooker. Layer With A Third Of The Noodles, A Third Of The Beef, A Third Of The Remaining Sauce And A Third Of The Cheeses. Repeat Layers Twice. Cover And Cook On Low For 4 Hours Or Until Cheese Is Melted And Lasagna Is Heated Through.