Prepare the water bath canner, jars, lids, and rings following the manufacturer's instructions.
In a 4-quart kettle, combine the water, vinegar, and salt. Bring to a simmer over medium-low heat. Whisk to dissolve the salt and keep hot until ready to use.
3 cups water, 4 cups vinegar (5% acidity), 1 ½ tbsp canning salt
Pack sterilized jars with prepared cauliflower. Don't be afraid to push the cauliflower in, as the cooking softens and shrinks them slightly. Add Serrano pepper, curry powder, turmeric, and cumin seed to each jar.
Pour the hot brine over the prepared jars, leaving ½-inch headspace at the top. Wipe the rim of each jar with a clean towel dipped in hot water to remove any drips. Place on prepared lids and rings, tightening to fingertip tightness.
Place jars in boiling water bath, ensuring the water covers the jars by 1 inch. Boil for 12 minutes.
Remove from water bath and allow to sit at room temperature for 8-12 hours. After cooled, remove rings to ensure a good seal. Store at room temperature for up to one year.