Set the tenderloin in the slow cooker insert and distribute the salt and black pepper over its surface. The seasoning should cover the exposed meat rather than collect in one spot.

Spread the applesauce across the pork, then empty the sauerkraut and all its brine over the fruit layer. The cabbage should blanket the meat, with liquid gathering beneath it.

Scatter the brown sugar across the cabbage in an even layer. Avoid thick piles so the sweetness can spread through the braising juices.

Pour the melted butter over the sugar-topped kraut, moving across the surface as you pour. The top should have buttery streaks rather than one concentrated puddle.

Cover and cook on low for about 8 hours, checking the thickest part of the pork with a thermometer for this recipe’s target of at least 160 °F. The kraut should look softened and slightly translucent, but use the thermometer rather than appearance to judge the meat.

Fold the cooked cabbage through the liquid at the bottom of the insert before serving. The finished kraut should glisten with evenly mixed buttery juices.