Sauté Aromatics
Heat the olive oil in a large saucepan over medium heat. Add the chopped onion and sauté until softened, about 3-4 minutes. Add the minced garlic and cook for 1 minute, stirring frequently.
Add Tomato Base
Stir in the tomato paste and cook for 1-2 minutes to deepen its flavor. Then, add the crushed tomatoes, diced tomatoes, sugar, oregano, basil, red pepper flakes (if using), and the bay leaf. Stir to combine.
Simmer the Sauce
Bring the mixture to a gentle boil, then reduce the heat to low. Cover partially and let the sauce simmer for 20-30 minutes, stirring occasionally, until thickened and flavors meld together.
Season to Taste
Remove the bay leaf and taste the sauce. Add salt and black pepper as needed. For a smoother texture, blend the sauce using an immersion blender or transfer it to a regular blender (optional).
Finish with Fresh Basil
Stir in fresh basil leaves for a burst of brightness just before serving.
Serve
Toss the sauce with cooked spaghetti or your favorite pasta. Garnish with grated Parmesan cheese and a drizzle of olive oil, if desired.