Place a large saucepan over medium heat and add the olive oil. Allow it to warm gently until it shimmers slightly. This step builds a flavorful base for the entire marinara sauce.

Add the finely chopped onion to the warm oil. Cook for 5 to 7 minutes, stirring occasionally, until the onion becomes soft and translucent, releasing natural sweetness and enhancing the sauce’s depth.

Stir in the minced garlic and cook for another minute until fragrant. Be careful not to let it brown, as burnt garlic can create bitterness and affect the overall flavor of the sauce.

Pour in the canned whole peeled tomatoes along with their juices. Use a wooden spoon to gently break the tomatoes into smaller pieces, creating a rustic and comforting texture for the marinara sauce.

Stir in the tomato paste, dried oregano, red pepper flakes, salt, black pepper, and optional sugar. These seasonings enhance the natural tomato flavor and create a balanced, savory sauce with subtle warmth.

Reduce the heat to low and allow the sauce to simmer uncovered for 30 to 35 minutes. Stir occasionally to prevent sticking while the sauce thickens and the flavors deepen beautifully.

For a smoother texture, use an immersion blender directly in the pot or carefully transfer the sauce to a blender. If you prefer a rustic texture, simply skip this step.

Stir in the chopped fresh basil and optional butter to finish the sauce. The basil adds freshness, while the butter provides a silky, rich finish. Taste and adjust seasoning before serving.