Preheat the oven to 450°F then place the stemmed jalapenos and chopped onion on a baking sheet
Drizzle them with olive oil and a pinch of kosher salt
Roast for 15 minutes or until they start to brown
Blending the Sauce
Add roasted jalapenos, onions and remaining ingredients to food processor and blend on high for 60 seconds
Taste and check salt level. Adjust if needed
Notes
Adding ¼ - ½ cup sour cream is optional to make the sauce creamier or cool down the spice if it's too spicy for you.You can also add water or oil, a tablespoon at a time if sauce is too thick after chilling.