Begin by chopping the red cabbage. Place the cabbage quarters into the bowl of a large food processor fitted with an S-blade. Pulse short and quick until the cabbage is chopped into small, confetti-sized pieces.

Transfer the mixture to a large colander, allowing excess moisture to drain.

Rinse the chopped cabbage under cold running water and shake the colander vigorously to remove excess water.

Transfer the drained cabbage to a large mixing bowl. Add the sumac and kosher salt, and massage the mixture with your hands to ensure even distribution. Let sit for about 15 minutes.

Pour in the distilled white vinegar and water, mixing well to combine.

Transfer the mixture to a large mason jar or several smaller jars, packing the vegetables down tightly to ensure they are submerged in the brine.

Seal with a lid and refrigerate for at least 3 hours before serving. The pickled cabbage will stay fresh for up to 4 weeks.