Heat the olive oil in a medium saucepan over medium heat. Once hot, add the finely chopped onion and sauté for about 5–7 minutes, until the onion is translucent and soft. Stir in the minced garlic and cook for another minute, just until fragrant—do not let it brown.

Pour in the whole peeled tomatoes with their juices. Use a wooden spoon to gently crush the tomatoes in the pan (or pre-crush them by hand before adding). Stir in the tomato paste until fully incorporated, which helps thicken and deepen the sauce.

Add the sugar, fresh basil, a generous pinch of salt, and a few cracks of black pepper. Reduce the heat to low and let the sauce simmer uncovered for about 25–30 minutes, stirring occasionally. This allows the flavors to meld and the sauce to thicken.

Taste and adjust seasoning with more salt or pepper if needed. If you prefer a smoother sauce, use an immersion blender directly in the pot or blend in a regular blender in batches (cool slightly first). Otherwise, leave it rustic and chunky.