Make the Sloppy Joe Mixture: Chop the onion and bell pepper. In a nonstick skillet over medium-high heat, cook the ground beef, onion, and green peppers until browned, about 6–8 minutes. Reduce to medium heat if the beef cooks too quickly. If you’re not using lean ground beef, drain any excess grease. Once browned, add ketchup, mustard, brown sugar, garlic, smoked paprika, salt, and pepper. Reduce heat to low and let simmer, stirring occasionally, for about 10 minutes to meld the flavors.
1 pound ground beef, ¼ cup onion, ¼ cup green bell pepper, ¾ cup ketchup, 1 tablespoon mustard, 1 tablespoon brown sugar, 1 teaspoon garlic, 1 teaspoon smoked paprika, ½ teaspoon salt, ¼ teaspoon pepper