In a medium bowl, whisk together the tomato sauce and crushed tomatoes until smooth.
Add the garlic, oregano, basil, onion powder, parmesan, sugar (if using), and red pepper flakes.
Season with salt and freshly ground black pepper to taste.
Drizzle in the olive oil and stir well to combine.
Let the sauce sit for at least 10 minutes to allow the flavors to meld.
Use immediately, or store in the refrigerator for up to 3 days. The sauce also freezes well for up to 3 months.