Step 1

For The Brine: In a large bowl, whisk together water and salt until dissolved, at least 30 seconds. In a wide-mouth, 1-quart canning jar, add peppers, garlic, and cumin seeds. Pour brine into jar and stir gently to combine. Cover surface loosely with plastic wrap, ensuring full contact, and place a smaller lid on top of plastic. Seal jar with airlock lid following manufacturer's instructions.

Step 2

Store mixture in dark area away from sun and let ferment, maintaining an ambient temperature between 55°F (13°C) and 75°F (24°C) for 10 days; check mixture daily for signs of gas formation (this is a good sign). Starting on the 10th day, taste peppers or garlic daily until they taste sour like dill pickles; the total fermentation time can take anywhere from 10 to 28 days.

Step 3

For The Sauce: Drain solids through fine-mesh strainer set over large nonreactive bowl; reserve liquid. You should have roughly 9 1/4 ounces (265g) solids. Transfer solids to a blender. Add 1 cup (240ml) reserved brine along with the vinegar and sugar. Discard remaining brine. Blend peppers on high speed until smooth and emulsified, 1 to 2 minutes. Season with salt. Measure sauce's pH using strips or pH-meter to ensure it is at or below a pH of 3.4; if it is too high, lower pH to 3.4 with more vinegar as needed.

Step 4

Strain blended sauce back through fine-mesh strainer set over bowl or large container, pressing on solids to extract as much liquid as possible; reserve solids for another use (see note).

Step 5

Optionally, if using xanthan gum: Rinse out blender jar. Transfer strained sauce back to blender. With blender running on high speed, slowly sprinkle in xanthan gum to avoid clumping; blend until mixture is slightly thickened, about 1 minute.

Step 6

Transfer strained hot sauce to glass bottles or jar, cover, and keep refrigerated until ready to use. Sauce can be refrigerated for up to 3 months.