Combine ground beef, breadcrumbs, eggs, garlic, oregano, parsley, and salt in a large bowl
Form mixture into 1.5-inch meatballs using wet hands
Heat olive oil in a skillet over medium heat; brown meatballs until no longer pink
In a large pot, sauté onion in olive oil until softened
Add crushed tomatoes, oregano, parsley, and salt to the pot; bring to a simmer
Gently place browned meatballs into sauce
Simmer uncovered over low heat for 30 minutes
Stir in grated cheese during the final 5 minutes
Boil water in a pot; add salt, then spaghetti
Cook pasta to al dente (around 8-10 minutes)
Reserve 1/2 cup pasta water, then drain
Toss cooked spaghetti with meatball sauce and reserved water until glossy