Prep the apples: Peel the apples (optional), remove the cores, and cut into large chunks.
Add to pot: Put the apples in a large, heavy pot. Add the cinnamon, lemon juice, brown sugar, water, and vanilla (if using). Stir to coat.
Cook: Cover and cook over medium-low heat for 25 to 35 minutes, stirring occasionally, until the apples are very soft. Add more water if the pot looks dry.
Taste: Remove the lid and let cool for a few minutes. Taste and add more sweetener if desired, starting with 1 teaspoon.
Blend or mash: Blend until smooth with an immersion blender or regular blender, or mash with a potato masher for chunky applesauce.
Thicken if needed: If too watery, simmer uncovered for a few more minutes, stirring often.