Rump cap is considered by many to be the best cut for roast beef—prime rib quality without the price tag. This recipe uses a safe, straightforward method that ends with edge-to-edge medium rare and a golden, crackly fat cap. Scoring and rendering the fat cap golden makes it nicer to eat and look better. A meat thermometer is essential to ensure it's not overcooked, as rump cap is less forgiving than prime rib or tenderloin.