Pour tomatoes and juice into a large bowl. Using your clean fingers, squish the tomatoes to break them up.

In a medium pot or Dutch oven, over medium high heat, add olive oil. Once the oil is shimmering add chopped onion and saute for 3 to 5 minutes or until the onions are softened. Lower the heat to medium, add garlic, and cook, stirring occasionally for another minute.

Add a teaspoon of tomato paste and cook, stirring for 1 minute.

Add the crushed tomatoes and stir everything together. At this point, you can use a potato masher to mash the tomatoes up even more for a smoother consistency. 

Add chicken stock, salt, sugar, and red pepper flakes to sauce, and simmer for 25 to 30 minutes.

Add diced basil and simmer for an additional 5 minutes to complete the sauce.

Store in a sealed container in the refrigerator and warm in a pot on the stove or in a bowl in the microwave.