Heat oven to 325° F. Coat a 6-indentation doughnut pan with nonstick cooking spray.
In large bowl, whisk flour, baking soda and salt. In a small bowl, whisk buttermilk, sugar, egg, melted butter and vanilla extract until smooth. Add milk mixture to flour mixture; whisk until smooth.
Spoon batter into a large resealable ziptop bag. Cut off a corner and squeeze batter into prepared indents, about 2/3 full. Smooth tops. Bake at 325° F for 13 minutes, until doughnuts spring back when lightly pressed. Cool in pan on rack 3 minutes, then carefully turn out onto rack to cool.
Lemon Glaze: Combine 2 tablespoons fresh lemon juice and 1 1/2 cups powdered sugar, stirring well with a whisk. Dip 1 side of the cooled doughnuts into glaze; let cool on a rack, glazed side up. I allowed the glaze to cool and dipped the doughnut three times this way to make a thicker glaze on top of the doughnut.
Cinnamon-sugar doughnuts: Combine 1 tablespoon ground cinnamon and 2 tablespoons sugar. Brush a small amount of melted butter on the top of the doughnut, and dip the top of the still-warm doughnuts in cinnamon-sugar to coat. Let cool on rack.
Powdered doughnuts: Place 1/4 cup powdered sugar in a sifter and gently sift over cooled doughnuts.
Chocolate-frosted doughnuts: Combine 1 cup powdered sugar, 1 tablespoon unsweetened cocoa powder, and 2 tablespoons milk. Stir until smooth. Dip cooled doughnuts into bowl and allow excess icing to drip back into bowl. Transfer to rack.
Doughnuts may be topped with sprinkles, coconut or mini chips, if desired.
Notes
*Cook’s notes: I used 1 tablespoon powdered buttermilk that I reconstituted with 7 tablespoons 2% milk. The powered buttermilk has a tendency to clump together, so I break off a chunk and put the chunk in the coffee grinder. Give it a whirl until it is a fine powder. Allow the powder to settle before opening the grinder. Then, measure out the desired amount of powder. Store any remaining powder back in the bag of buttermilk.Adapted from From Family Circle