1Heat oven to 350°F. Place Reynolds Baking Cups in each of 17 regular-size muffin cups. In large bowl, stir cupcake ingredients just until dry ingredients are moistened. Spoon batter evenly into muffin cups.
2Bake 16 to 18 minutes or until toothpick inserted in center comes out clean. Remove from pan to cooling rack. Cool completely, about 30 minutes.
3In 1-quart saucepan, heat 1/3 cup butter over medium heat just until light brown, stirring occasionally. (Watch carefully because butter can burn quickly.) Remove from heat. Cool slightly, about 5 minutes.
4In medium bowl, beat butter, powdered sugar, vanilla and enough milk until smooth and spreadable. Spread frosting over cooled cupcakes.