In a large skillet, add butter and heat over medium-high heat. Once melted, add beef/turkey and cook until brown. Drain and set aside.
Add onions, bell pepper and garlic to skillet. Sauté until onions are translucent and bell pepper is soft, about 5 minutes.
Add cooked ground beef/turkey, ketchup, BBQ sauce, water, brown sugar, chili powder, cumin, dry mustard, Worcestershire sauce, salt and pepper to the skillet. Stir to combine all ingredients and simmer for 15-20 minutes.
Warm rolls on the stove for a few seconds then spread meat mixture over buns.