Wash, core and slice apples about 1/4 inch thick. Toss in a splash or two of lemon juice to keep apples fresh.
In a skillet over medium heat, melt butter. Add sliced apples. Cook just until tender, about 5-7 minutes. Stir regularly.
Add brown sugar, cinnamon, vanilla and salt. Stir to evenly distribute and coat all apples.
In a measuring cup, add cornstarch to cold water and stir until dissolved. Pour cornstarch mixture over apples. Stir to combine. Allow to cook at a low boil for another 3-5 minutes, stirring constantly until mixture is thick. Remove from heat and serve warm.