Preheat oven to 300° F (150°C).
Season meat with salt and pepper and place in a 9x13-inch pan; cover with onion. In a small bowl, combine ketchup, chili sauce, sugar, garlic and beer; pour mixture over meat. Cover with foil and bake for 4 hours.
Remove foil and bake uncovered for an additional 35 to 40 minutes. Remove meat from pan; let cool. Slice meat cross-grain.
Make gravy. With an immersion blender or a blender, blend all liquid from the pan. Cook and stir until thick. Return sliced meat to baking dish and reheat. Serve with gravy.
Servings: 6