In a large saucepan, add the onion, jalapeno and oil. Cook on medium heat until the vegetables have softened, 8-10 minutes.
Stir in the garlic, chili powder, cumin, oregano, sugar and salt and cook until fragrant, 30 seconds to 1 minute. Add the tomato sauce and chicken stock and stir to combine. Bring to a simmer.
Reduce heat to low and simmer for 15 minutes until the sauce has thickened slightly. (Optional but recommended: Carefully pour the sauce into a blender and blend until smooth.) Add more salt, if necessary (I usually add another pinch or two).
Use the sauce in enchiladas, tacos, quesadillas and more. Enjoy!