Sear the Roast: Heat 2 tablespoons of oil in a large skillet over medium-high heat. Sear the beef sirloin roast for 3-5 minutes on each side until nicely browned.

Prepare Broth Mixture: In a bowl, whisk together brown sugar, apple cider vinegar, soy sauce, Worcestershire sauce, cream of mushroom soup, half of the dry onion soup mix, and beef broth. Pour this mixture over the seared roast in the slow cooker.

Prepare Vegetables: Peel and cut the carrots into 1-inch pieces, and quarter the red potatoes.

Coat Vegetables: In a resealable plastic bag, add carrots and potatoes with the remaining half of the dry onion soup mix. Seal and shake to coat evenly.

Combine in Slow Cooker: Add the coated vegetables around the roast in the slow cooker.

Cook: Cover and cook on high for 5-6 hours or low for 8-10 hours until the roast is fork-tender.

Serve and Enjoy: Remove the roast and veggies from the slow cooker. Let the roast rest before slicing and serve with the broth.