My favorite is a pot roast with cut up vegetables. Use a cut of meat like a seven bone roast that will fit the dutch oven. (you can also do this in a roasting pan, but I get better results with the cast iron. I brown the roast on both sides on top of the stove in a small amount of oil. I'm using my cast iron dutch oven for this or do it in a skillet.
Sprinkle a pkg of beefy onion soup on top and add about two cups water. With the lid on, bake for about an hour at 325/350. (all ovens are a little different)
Cut up vegetables in large chunks, (onions, celery, carrots, potatoes) and dump over roast, salt and pepper. Add a little more water if needed and cook another hour. Sometimes I'll add cabbage wedges (if there is room) about thirty minutes into the second hour.
yum
I also like a tri-tip roast. That you just cook in an open pan uncovered. I gauge it about 18 min a pound at 350 for med. Let rest about 10 min. before slicing. Cut against the grain for tenderness.
The drippings at the bottom of the pan are good for making gravy with. Pour off any excess oil and add a cup of water. Stir around the pan scraping up any bits of roast and pour into a sauce pan. You can add this to a rue of butter and flour or I use corn starch dissolved into a cup of water. Stir until thickened.
I'm not a fan of marinades or rubs, but a lot of people are.