Put onion with oil in a medium pot over medium heat and cook until onion softens, about 5 minutes. Meanwhile, put tomatoes, garlic, and chiles in a blender and pulse a few times (leave the mixture a little chunky).
Pour tomato mixture into pot with onions and cook 5 minutes over high heat to thicken. Taste and add hot sauce if you like.
Note: Nutritional analysis is per serving.