You can use pasta sauce (marinara), tomato sauce, or canned crushed tomatoes.
If you'd like a bit of spice, jalapenos would be a nice addition.
Substitute the ground beef with ground turkey or sausage and the bacon with turkey bacon if desired. For the beef, brown it thoroughly before adding to the casserole dish. Season it as you'd like while browning. Garlic powder, salt, and pepper are our go-to's.