Bottom round roast in oven - Preheat oven to 450 degrees F. Mix together seasonings. Pat outside of meat with paper towels. Coat outside, bottom, top, sides well with dry rub so it is well coated.
Set inside a baking dish or on a sheet pan with high sides, with a rack underneath so it isn't sitting directly on the bottom. Bake at 450 degrees F for 15 minutes, then lower temp to 325 degrees F and bake until center reaches 135 degrees F for medium rare = perfect temp. Remove and let it rest for 15 minutes before slicing against the grain.
Bottom round roast on stove top - Mix dry rub ingredients, pat dry meat and spread all over. In a Dutch oven, heat 2 tbsp olive or vegetable oil over medium-high heat. Once hot, add the roast to the pot. Sear on all sides until it develops a deep brown crust. Remove from pot and set aside.
In the pot add 5-6 chopped onions and 3 tbsp. minced garlic to the pot and sauté for a few minutes until they become fragrant and translucent. Spread across the bottom and set the roast on top of your bed of onions. Pour 1 tbsp white vinegar on top + 1/4 cup beef broth.
Reduce heat to low, cover the pot with a lid, and let the roast simmer gently. You can maintain a low simmer by adjusting the heat as needed. Cook for about 3 hours for a 2-3 pound roast, or until it is fork-tender. Check to add more liquid if necessary to prevent it from drying out. When done, remove it from the pot and let it rest for about 10-15 minutes before slicing against the grain.
Slow cooker bottom round roast - Mix together seasonings and generously sprinkle on both sides of the roast. Place roast in the bottom of a Crockpot. Add quartered potatoes, peeled chunks of carrots, and 2 sliced onions around the meat.
Whisk together 1 cup beef broth + packet of dry gravy mix and pour on top of vegetables and roast. Cover and cook on low for 5-6 hours or high for 2-3 hours or until internal temperature reaches 140 degrees F.
When cooking is complete, remove roast and set aside on a serving plate. Use a slotted spoon to remove vegetables and place onto the serving plate with the roast. Cover with foil to keep warm. Place remaining juice from the slow cooker into a saucepan over high heat, once boiling add 1 tbsp. flour and whisk until gravy is thick. Serve on top of sliced beef roast against the grain.