Preheat oven to 250℉.
Rinse beef under cold running water. Pat dry with a paper towel.
Using a fork prick roast all over on both sides to help tenderize the beef.
Season both sides of roast with salt and pepper.
Heat butter and olive oil in a large oven safe pot over medium high heat.
Sear roast on both sides until edges are charred, about 3-4 minutes per side.
Remove pot from heat and add diced onions.
Combine hot water and bouillon, stir until bouillon is completely dissolved.
Stir together bouillon broth, ketchup, red wine vinegar, minced garlic, brown sugar, and Worcestershire sauce to make the sauce.
Pour sauce into the pot over the seared beef and diced onions.
Cover pot with a lid and place it in the oven.
Cook, covered, for 3 hours.
Meat is done when it shreds easily with a fork or tongs.
Serve shredded beef with gravy over a bed of mashed potatoes.