To a large heavy bottomed skillet or pan, add 1/2 the butter. Once melted, sear the meat evenly on all sides. Set aside.
Add the rest of the butter. Once melted add the onions & garlic powder. Stir & cook until the onions are soft and beginning to caramelize.
Stir in the mushrooms, cream of mushroom soup, and water. Whisk together until evenly combined. Stir in the gravy master.
Transfer the meat back to the pot, bring the gravy to a boil, and then lower the heat all the way so it's just at a slow simmer. Cover the pot, and let the roast cook for 3-4 hours.
Slice the meat thinly, serve and enjoy with the gravy.
The gravy will be very thick in the pot when first prepared, but don't worry. It will naturally thin to a perfect consistency with just the little bit of water and the juice from the meat while cooking.