Put the garlic, unpeeled tomatoes, and chiles into a blender jar and blend to a slightly textured sauce.
Set aside.
Heat the oil in a heavy frying pan, add the onion, and cook gently until translucent-about 3 minutes.
Add the blended ingredients and salt and cook over high heat, scraping the bottom of the pan from time to time, until slightly reduced and thickened-about 8 minutes.
There will be flecks of brown in the sauce thats okay; it means flavor and looks more interesting.