Melt butter in a large skillet or saucepan over medium heat.

Add apples and cook, stirring constantly, until almost tender, 6 to 7 minutes.

Mix water and cornstarch together in a small bowl until cornstarch is dissolved; pour over apples. Stir in brown sugar and cinnamon. Bring to a boil for 2 minutes, stirring occasionally, until the sauce thickens.

Remove from heat and serve warm.