Preheat oven to 400°.
Lightly spoon flour into a dry measuring cup; level with a knife. Combine flour and next 5 ingredients (flour through eggs) in a blender; process until smooth. Chill 30 minutes.
Arrange nectarines in a 13 x 9-inch baking dish coated with cooking spray. Pour batter over fruit. Bake at 400° 35 minutes or until set.