Sloppy Joe Meatball Bake

1 . Stage

In a large bowl, combine ground beef, egg, panko, milk, 1/4 cup onion, 1 teaspoon Worcestershire sauce, 1 1/4 teaspoons kosher salt, and 1/4 teaspoon black pepper. Using a scoop or spoon, scoop meat mixture, roll into about 33 (1 1/2"; 2 tbsp.) balls, and arrange on a plate.

2 . Stage

Preheat oven to broil on high. In a large Dutch oven or ovenproof pot over medium-high heat, heat 2 tablespoons oil. Arrange meatballs in skillet in a single layer. Cook, turning occasionally, until seared on all sides, 7 to 9 minutes total. Transfer meatballs to a plate; discard grease in pot.

3 . Stage

Return pot to medium heat and add bell pepper, garlic, and remaining onion and 1 tablespoon oil. Cook, stirring occasionally, until vegetables are tender, 8 to 10 minutes. Add tomato sauce, ketchup, water, vinegar, brown sugar, mustard, and remaining 1 tablespoon Worcestershire. Using a wooden spoon, scrape any bits from bottom of pot. Return meatballs to pot and bring to a simmer. Cook, stirring occasionally, until sauce is slightly thickened and meatballs are cooked through, 4 to 6 minutes. Remove pot from heat and sprinkle with cheese.

4 . Stage

Broil until cheese is bubbly and golden, about 2 minutes.