Heat the olive oil in a saucepan over medium heat until shimmering.
Add the chopped onion to the pan and sauté for 5 minutes, stirring occasionally until translucent and fragrant.
Stir in the minced garlic and cook for another 30 seconds, just until fragrant and slightly golden.
Add the chopped tomatoes to the pan, stirring to combine, and bring to a simmer.
Reduce the heat to low and let the mixture simmer uncovered for about 20-25 minutes, stirring occasionally, until the tomatoes break down and the sauce thickens.
Stir in the chopped basil, salt, and black pepper, then cook for an additional 5 minutes to let the flavors meld.
Optional: use an immersion blender to puree the sauce until smooth, or leave it chunky based on preference.
Once the sauce has reached your desired consistency and aroma, remove from heat and serve over your favorite pasta or dish.