Preheat oven to 400°.
Place apple on paper towels; squeeze until barely moist. Lightly spoon flour into dry measuring cups; level with a knife. Combine the flour and next 6 ingredients (flour through cinnamon) in a medium bowl; stir with a whisk. Make a well in center of mixture. Combine milk, oil, vanilla, yogurt, and egg; stir well with a whisk. Add to flour mixture, stirring just until moist. Stir in apple.
Spoon batter into 12 muffin cups coated with cooking spray. Bake at 400° for 20 minutes or until muffins spring back when touched lightly in center. Remove muffins from pans immediately; place on a wire rack.