Begin by removing the outer leaves of the cabbage and cutting it into quarters.

Using a sharp knife or a mandoline, finely shred the cabbage into thin strips.

In a large bowl, combine the shredded cabbage and salt.

With clean hands, massage the cabbage for about 5-10 minutes until it becomes soft and watery.

Stir in the sliced onion, grated apple, and caraway seeds if using.

Transfer the mixture into a fermentation jar, pressing down firmly to eliminate air pockets.

Place a weight on top of the cabbage to keep it submerged in its brine.

Cover the jar loosely with a lid or cloth and let it sit at room temperature for 1 to 4 weeks.