Peel and core the apples.
Cut them into 1-inch chunks to make sure they cook evenly.
Combine the apple chunks with the lemon juice, apple juice, brown sugar, cinnamon, and kosher salt.
Stir the mixture well in a 4- to 6-quart slow cooker.
Cover the slow cooker with a lid.
Set it to cook on high for 4 hours. Stir halfway through to ensure even cooking.
Once the apples are soft, use an immersion blender to puree the mixture.
Adjust the consistency according to your preference.
Allow the applesauce to cool completely at room temperature.
Refrigerate it if you'd like it chilled.