Place the tomatoes and garlic in a medium saucepan, cover with water and bring to a boil over medium-high heat. Reduce heat to medium and simmer for 10 to 15 minutes until the tomatoes are completely smooth, cooked and mushy.
Place tomatoes and garlic in a blender along with the onion, salt, and black pepper and process until completely smooth.
Heat the oil in medium saucepan, set over medium heat. Once the oil is hot, pour in the tomato sauce, cover with a lid partially and simmer for 5 to 6 minutes, stirring here and there. Add the chicken broth, stir and cook for another 6 to 8 minutes, until well seasoned and lightly thickened.