Heat oven to 350°F. Place Reynolds Baking Cup in each of 16 regular-size muffin cups. In large bowl, beat cake mix, cinnamon, nutmeg, water, 1/2 cup butter, the vanilla and eggs with electric mixer on low speed 30 seconds, then on medium speed 2 minutes, scraping bowl occasionally. Stir in chopped apple. Divide batter evenly among muffin cups.