Prepare the Fresno chiles and red bell peppers by cutting off the stems and removing the seeds and piths. Remove the skin from the garlic and onions.
Heat a cast iron skillet to medium-high heat and add a thin layer of oil to the pan. Roast red bell peppers, white onion, and Fresno chilis until the vegetables are charred, about 6-8 minutes. During the final 2 minutes, add in the garlic until browned.
Add the charred peppers, onions, and garlic to a blender along with the smoked paprika, vinegar, and salt.
Blend until smooth and let cool. If you’re having trouble blending the hot sauce to the right consistency, add 1 Tbsp. of water to adjust to the desired consistency.
Season to taste by adding more salt if necessary.
Add into hot sauce bottles and store in refrigerator.
Notes
Substitutions or modifications:
White onion or shallots can be used in place of the yellow onion
Red jalapeños are a great substitute for Fresno peppers
Chipotle powder makes a great alternative to smoked paprika
Add 1/2 teaspoon of ground black pepper for another layer of spiciness