Letting this mixture sit for a couple days will just intensify the sauce even more.
Chop the chiles. (Use gloves so you don’t end up crying because you rubbed your eyes.) After spraying the pan with cooking spray, sauté onions and garlic over medium-high heat for about 3 minutes.
Add the peppers, white vinegar, and salt, and bring to a simmer. Reduce the heat to low, cover, and simmer for another 8 or 9 minutes.
Pour mixture into a food processor and purée until smooth. Pour into a container and let it cool uncovered. Cover with an airtight lid and refrigerate for a few days.