Brown the butter: Melt the butter in a skillet or small saucepan over medium heat. Swirl or stir the butter with a wooden spoon as it starts to foam and sputter. Remove the butter from the heat as soon as it begins to turn golden brown and smells nutty, about 1 minute.
Add the apples, sage, 1/2 teaspoon salt, and 1/8 teaspoon pepper. Cook, stirring, until the apples are just tender, about 4 minutes. Serve with pork or chicken.