Step 1: Make the Meatball : Mixture In a large bowl, combine ground beef, ground pork, breadcrumbs, Parmesan, parsley, eggs, garlic, salt, pepper, oregano, and red pepper flakes.Mix gently until just combined — do not overmix or meatballs will be dense.
Step 2: Shape the Meatballs : Roll mixture into golf ball-sized meatballs (about 1.5 inches in diameter). Place on a plate or baking sheet.
Step 3: Brown the Meatballs : Heat olive oil in a large skillet or Dutch oven over medium heat.Add meatballs in batches, browning on all sides (about 5 minutes total). Remove meatballs and set aside (they will finish cooking in the sauce).
Step 4: Make the Marinara Sauce : In the same pan, add a little more olive oil if needed.Sauté onion until softened (about 3–4 minutes). Add garlic and cook 30 seconds until fragrant.Stir in crushed tomatoes, tomato sauce, basil, oregano, salt, pepper, and sugar (if using). Simmer for 10 minutes.
Step 5: Simmer Meatballs in Sauce : Gently return meatballs to the sauce.Cover and simmer for 20 minutes, until meatballs are cooked through and flavors meld.
Step 6: Cook the Spaghetti : Meanwhile, bring a large pot of salted water to a boil.Cook spaghetti according to package instructions until al dente. Drain and toss with a little olive oil to prevent sticking.