In a large bowl, combine the ground beef, onion, garlic, breadcrumbs, milk, egg, Worcestershire sauce, ketchup, thyme, salt, and black pepper. Mix well.
Roll the mixture into meatballs, about 1-2 inches in diameter, and place them on a baking sheet lined with parchment paper.
Bake the meatballs in the preheated oven for 20-25 minutes, or until they are cooked through and browned.
While the meatballs are cooking, prepare the sauce. In a large skillet, sauté the onion, garlic, and bell pepper until softened, about 5 minutes.
Add the diced tomatoes, tomato paste, thyme, salt, black pepper, and cayenne pepper to the skillet. Stir well to combine.
Add the cooked meatballs to the skillet with the sauce, and let simmer for 5-10 minutes.
Stir in the chopped parsley just before serving.
Notes
Tips and Tricks
Use a baking sheet lined with parchment paper to make the meatballs as it prevents sticking and makes for easy cleanup.If the meatball mixture is too dry, add a little more milk. If it is too wet, add more breadcrumbs.For a thicker sauce, add a tablespoon of cornstarch mixed with a tablespoon of water to the sauce and stir until thickened.Serve the meatballs with rice or mashed potatoes to make a complete meal.