Preheat oven to 400°.
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour and next 4 ingredients (flour through salt) in a large bowl, stirring with a whisk. Make a well in center of mixture. Combine milk, eggs, and butter in a small bowl, stirring with a whisk. Add to flour mixture, stirring just until moist. Spoon batter into a 13 x 9-inch baking pan coated with cooking spray. Bake at 400° for 20 minutes. Cool in pan 10 minutes. Remove from pan; cool completely on a wire rack.