Weigh or lightly spoon flour into a dry measuring cup; level with a knife. Combine flour and next 5 ingredients (through salt) in a bowl, stirring well with a whisk. Make a well in center of flour mixture. Add milk mixture; stir just until moist.
Stir in raspberries. Spoon into 12 muffin cups coated with cooking spray. Sprinkle muffins evenly with 1 tablespoon sugar.
Bake at 400° for 13 minutes or until a wooden pick inserted in center comes out with moist crumbs clinging. Remove muffins from tins; cool on a wire rack.