Spaghetti and Juicy Lucy Meatballs

Name: Spaghetti and Juicy Lucy Meatballs
Ingredients: 1 teaspoon kosher salt, plus more for seasoning; 3 tablespoons (40 grams) extra-virgin olive oil, plus more for drizzling; 1/2 large onion (5 1/2 ounces/160 grams), sliced; 5 garlic cloves, chopped; 1 teaspoon dried oregano; 1/2 teaspoon crushed red pepper flakes; One 28-ounce (794 grams) can whole plum or San Marzano tomatoes, crushed by hand; One 15-ounce (425 grams) can tomato sauce; 1 pound (453 grams) spaghetti; 1/4 cup (15 grams) fresh basil leaves, torn; 1/2 cup (40 grams) grated Parmesan cheese, plus more for serving; Meatballs (recipe follows); 1 pound (453 grams) 80/20 ground beef; 1 pound (453 grams) hot Italian sausage, removed from casings; 1 1/2 teaspoons kosher salt; 2 large eggs, beaten; 1 cup (84 grams) plain dry breadcrumbs; 1 cup (40 grams) grated Parmesan cheese; 1/2 large onion (5 1/2 ounces/160 grams), grated on the coarse holes of a box grater; 1/4 cup (15 grams) chopped fresh Italian parsley; 2 garlic cloves, chopped; 8 small mozzarella balls/ciliegine (about 15 grams each)