Preheat the oven to 350 F and grease donut pans well with baking spray.
In a large mixing bowl, add the sugars and lemon zest. Use your fingertips to rub the zest into the sugars. This helps to bring out the lemon flavor.
Add the vanilla extract, sour cream, egg, lemon juice, and oil. Whisk to combine.
Use a spatula to stir the flour, baking powder, baking soda and salt into the wet ingredients. Stir just til combined. Do not overmix.
Use a piping bag or zip lock bag or spoon to equally fill the donut molds to just about ¾ full.
Bake 10-13 minutes unti a toothpick comes out clean when inserted in a donut. Let cool in the pans for 10 minutes then remove from pan and let donuts cool completely on wire rack.
Lemon Sugar Coating
In a shallow bowl or pie pan, combine the sugar with lemon zest. Use your fingertips to rub the zest into the sugars. This helps to bring out the lemon flavor and helps to incorporate the zest into the sugar.
Brush the cooled donuts with melted butter, vegetable, canola, or olive oil (extra virgin or regular).
Place one donut in the bowl of sugar. Gently rub the bottom and sides of the donut around in a circle to coat. Sprinkle sugar on the top. Set donuts on wire rack.
Notes
Filling the donut pans. I like to transfer the batter into a piping bag or a large zip lock bag. Seal the end then snip off the end (or a corner if using a zip lock bag) and pipe the batter into the donut pans. You can also simply spoon the batter into the donut pans. Storage: These baked lemon donuts are at their freshest and most flavorful the day they’re made. Store leftovers in an airtight container at room temperature for a few days or in the refrigerator for up to 1 week.