Heat olive oil in a large pot or Dutch oven over medium heat. Once the oil is shimmering, add the finely diced onion. Cook until the onion becomes translucent, stirring occasionally to prevent burning. This usually takes about 5 to 7 minutes. You'll know it's ready when it softens and starts to smell sweet.
Next, add the garlic and stir for 30 to 60 seconds. Keep an eye on it; you don't want the garlic to brown too much or become bitter. The goal is to release its fragrant aroma.
Now, it’s time to add your canned ingredients. Pour in the stewed tomatoes, crushed tomatoes, and tomato paste. Stir everything together, allowing the ingredients to mingle and combine.
Pour in the chicken broth. This will help keep the sauce moist and add another layer of flavor. Stir the mixture until it's well combined.
Now, add in the chopped fresh parsley, granulated sugar, dried oregano, dried basil, salt, and ground black pepper. These spices are what make the sauce sing! Mix everything well to ensure the spices are distributed evenly.
Bring the sauce to a gentle simmer. Once it starts bubbling, lower the heat to maintain a soft simmer. Cover the pot and let it cook for 20 to 30 minutes; if you have time, allowing it to simmer longer, even up to 2 hours, will deepen the flavors.
After simmering, if you want a smoother sauce, use an immersion blender to blend the sauce to your desired consistency. If you prefer a chunky texture, simply use a wooden spoon to break down some of the larger tomato pieces. Adjust the seasoning if necessary.
Once you’ve reached your desired consistency and flavor, remove the sauce from the heat. It’s now ready to serve!