Heat olive oil in a large saucepan over medium heat.
Add the chopped onion and sauté until translucent, about 5 minutes.
Stir in the minced garlic and cook for another minute until fragrant.
Pour in the whole tomatoes, crushing them with your hands or a spoon as you add.
Add sugar, dried oregano, salt, and pepper. Stir well to combine all ingredients.
Bring the sauce to a simmer, then reduce heat. Cover and let it cook for 30-45 minutes, stirring occasionally.
Taste and adjust seasoning if necessary.
Remove from heat and stir in chopped fresh basil just before serving.
