how to roast a rump roast tender
1 Put the Roast in the oven and sear for 20 minutes. 2  Then add the water, the chopped onion and reduce the temperature to 275 degrees. 3  Cook for 20 minutes per lb. 4  I like mine rare so that is what you will get if you cook for this period of time. Pre-Heat the oven to 500 degrees. 2  Prep the roast by making 4-5 slits in the roast and filling the holes with salt, pepper and 1/2 of a clove of Garlic. 3  Now Salt and Pepper the rest of the roast. 4  Put the Roast in the oven and sear for 20 minutes.