Peel and finely dice the apples. I like small pieces, about ¼" cubes (roughly).
In a medium pot, melt the butter over medium heat.
Add the chopped apple to the pot, cook until it starts releasing the juice, about 4-5 minutes.
As the apples are cooking, combine brown sugar, cornstarch, cinnamon, nutmeg, and salt in a small bowl.
Add dry mixture to the apples, toss to coat.
Simmer for a 5-10 more minutes, until the juice cooks off and starts to form a thick glaze.
Remove from heat, stir in vanilla, and allow to cool to room temperature.