Rump roast of beef is also called diamond cut, Manhattan roast, round roast and bottom round roast. While not as tender as some cuts of beef, it has enough marbling to either roast or braise. Cooking rump roast in a Dutch oven helps to retain flavor and moisture. Browning the rump roast in the Dutch oven before roasting or braising it helps to develop the flavor by caramelizing the surface of the meat. It also seals the surface of the meat by tightening proteins and pushing moisture in the meat toward the center. Braising the roast in a Dutch oven with a tight-fitting lid allows you to use less liquid, so the meat doesn't become gray and stringy because it boils in the cooking liquid.
Remove roast out from the refrigerator and allow it to come to room temperature. Preheat the oven to 325 degrees Fahrenheit.
Season the rump roast on all sides with salt and pepper.
Heat the oil in your Dutch oven over medium-high heat. When the oil is hot, brown the rump roast on all sides, turning it frequently with tongs.
Place onion and garlic around the roast. Add the bay leaf and thyme leaves. Pour the beef stock and beer over the rump roast.
Put the lid on the Dutch oven and put the roast in your oven. Bake for two to three hours until the meat is fork-tender.
Preheat the oven to 250 degrees Fahrenheit. Remove the roast from the refrigerator and allow it to come to room temperature. Season the roast on all sides with salt and pepper.
Heat the Dutch oven over medium-high heat. Add 2 tbsp. of oil. Sear the roast on all sides, which takes about six minutes. Turn it frequently with tongs.
Remove the Dutch oven from the heat. Turn the roast fat side up.
Cook the roast in the oven, uncovered, until the internal temperature is 140 degrees Fahrenheit, measured with an instant-read thermometer inserted into the thickest part of the roast. Check the temperature after an hour of roasting. How long the roast needs to cook depends on its shape and size, as well as the temperature of the oven.
Remove the rump roast from the skillet and allow it to rest for 15 minutes, covered with foil. Cut thin slices across the grain of the meat.