Rump Roast

Let the Joint rest at room temperature for one hour. Trim fat off the rump roast if it’s too fatty.
When the rest time is up, preheat the oven to 275F (135C).
Heat the oil in a large cast iron Dutch oven over medium heat on the stovetop. Season the rump with salt and pepper, and brown it on all sides (2-5 minutes per side).

Peel an onion, slice it in half, then cut it into thin half-moons. Add it to the Dutch oven along with the thyme, garlic powder, and beef broth. If the roast has a fattier side, arrange it fatty side up.
Put the Dutch oven on a rack ⅔ down in the oven (or use the middle oven rack for large ovens). Do not cover the pot.
How long to cook a 3 lb rump joint in the oven? Cooking rump in the oven takes about 60 minutes for medium or medium-rare. Do not cook the rump for too long or it will get very tough!

The best way to check the doneness of a rump of beef roast is to use a meat thermometer. Here’s an internal rump roast temperature chart:
Doneness Internal Temperature
Rare 130-135F (54-57C)
Medium 140-145F (60-63C)
Medium Well 150F (66C)
Well Done 160F (71C)
8. After cooking, remove the rump roast from the pot. Tent the roast in foil and allow it to rest for 15-20 minutes before slicing thinly and serving. This gives the juices in the roast time to redistribute. (You can use the liquid in the bottom of the Dutch oven to serve the beef with au jus gravy.)