I'm a huge fan of roasted vegetables. They're easy, versatile, flavorful and make for amazing leftovers. You can blend them with chickpeas to make hummus, add them to a salad, eat them plain, or stick them in between 2 slices
The easiest lasagna ever includes three kinds of cheese simmering along with spaghetti sauce and ground beef. The slow cooker does everything but go to the store for you.