If you prefer, use 2 lb. ground beef instead of the roast; omit oil. Cook ground beef with onions and garlic until meat is browned. Drain off fat. Add cumin and ground ancho pepper; cook and stir 1 minute more. Transfer mixture to slow cooker. Stir in next five ingredients (through tomato paste). Cook and serve as directed.
Use a 6-qt. electric or stove-top pressure cooker. Sprinkle meat with black pepper. For electric cooker, use sauté setting to brown meat, one-third at a time, in oil; for stove-top cooker, brown meat, one-third at a time, in oil directly in pot. Stir in next nine ingredients (through tomato paste). Lock lid in place. Set electric cooker on high pressure to cook 20 minutes. For stove-top cooker, bring up to pressure over medium-high heat according to manufacturer's directions; reduce heat enough to maintain steady (but not excessive) pressure. Cook 20 minutes. Remove from heat. For electric or stove-top cooker, let stand to release pressure naturally, at least 15 minutes. If needed, carefully open steam vent to release any remaining pressure. Open lid carefully. Season to taste with salt and additional black pepper. Serve with desired toppings.