Line greased 15x10x3/4-inch pan with parchment or waxed paper. Grease and flour paper; set aside. Beat cake mix, eggs, yogurt and oil in large bowl with mixer 2 min. or until well blended; spread 3 cups into prepared pan. Tap pan gently on counter to remove any air bubbles. Pour remaining batter into 4 to 6 paper-lined muffin cups. Bake cake and cupcakes 15 min. or until toothpick inserted in centres comes out clean. Meanwhile, place large sheet of parchment paper on top of clean kitchen towel; sprinkle with icing sugar.