Tender baked beef meatballs tossed in a glossy sweet-and-tangy sauce made with ketchup, brown sugar, and apple cider vinegar. Perfect as a party appetizer or an easy weeknight dinner over rice or mashed potatoes.
Preheat oven to 400°F. Line a rimmed baking sheet with foil and set a wire rack on top. Lightly coat the rack with cooking spray.
In a bowl, stir together panko breadcrumbs and milk. Let sit 5 minutes to hydrate.
In a large bowl, combine ground beef, egg, onion, garlic, kosher salt, and black pepper. Add the soaked breadcrumbs and gently mix just until combined.
Shape the mixture into meatballs about 1.5 inches wide (roughly 24 meatballs). Place on the prepared rack.
Heat olive oil in a large skillet over medium-high heat. Sear meatballs in batches for 2 to 3 minutes, turning to brown on multiple sides. Return seared meatballs to the rack.
Bake meatballs for 12 to 15 minutes, or until cooked through and an instant-read thermometer reads 165°F.
Meanwhile, make the sauce: In a saucepan over medium heat, whisk together ketchup, brown sugar, apple cider vinegar, Worcestershire sauce, Dijon mustard, and red pepper flakes. Simmer for 3 to 4 minutes until glossy and slightly thickened.
Transfer baked meatballs to the saucepan and toss to coat. Simmer 2 to 3 minutes so the sauce clings well.
Garnish with chopped parsley and serve warm as an appetizer or over rice or mashed potatoes.
Notes
Make-ahead: Form meatballs up to 24 hours in advance and refrigerate. To freeze, bake fully, cool, and freeze in sauce for up to 2 months. Reheat covered at 325°F until hot. Adjust sweetness or tang by tweaking brown sugar and vinegar to taste.