In a medium mixing bowl combine ground chuck, breadcrumbs, milk, beaten egg, 1 teaspoon Italian seasoning, 1/2 teaspoon dried parsley, 1/4 teaspoon red chili flakes, 1/2 teaspoon onion powder, 1/4 teaspoon granulated garlic, 1 teaspoon salt, and 1/2 teaspoon ground black pepper; mix gently until just combined. Cover and refrigerate at least 30 minutes.
Heat 2 tablespoons olive oil in a large pot or Dutch oven over medium heat. Add the thick-sliced garlic and cook until soft and fragrant, about 1–2 minutes, then remove and set the garlic aside.
Add the canned tomato puree and diced tomatoes to the pot, then stir in 1½ teaspoons Italian seasoning, 1/2 teaspoon dried basil, 1/4 teaspoon red chili flakes, 2 teaspoons salt, and 1/2 teaspoon ground black pepper; reduce heat to low, cover, and simmer 25–30 minutes. Taste and add up to 1 tablespoon sugar if the sauce is too acidic.
Meanwhile preheat the oven to 425°F (220°C). Line a rimmed baking sheet with foil and spray with nonstick spray.
Remove the chilled meat mixture and form into 1½-inch meatballs. Place them on the prepared baking sheet and bake 10–15 minutes, until browned and cooked through.
While meatballs bake, cook the spaghetti according to package directions until al dente, then drain.
To serve, plate desired amount of spaghetti, spoon marinara sauce over the pasta, top with meatballs, and sprinkle with grated Parmesan and chopped fresh parsley.