Preheat oven to 350°F(180°C). Place 1/2 cup (1 stick/113g) of the butter and brown sugar in small saucepan. Cook on medium heat 2 minutes or until sugar is dissolved. Stir in 2 teaspoons (10ml) of the vanilla and 1 teaspoon (5ml) of the apple pie spice. Pour into 13x9-inch baking pan. Place apple slices in even layer in bottom of pan. Set aside.