Step 1

Prep. Preheat oven to 350 degrees with the rack in the center.  Prepare a loaf pan or 9 x 9 square cake pan with cooking spray.

Step 2

Wet ingredients. Combine the vegetable oil, eggs, and sugar in a large mixing bowl with an electric mixer until well combined.

Step 3

Dry ingredients and milk. Mix the flour, baking powder, and salt in a separate bowl and add to the sugar mixture 1/3 at a time, alternating with the milk and the sourdough starter.  Mix on low until just combined.  Stir in the lemon juice and lemon zest by hand.  Pour the batter into the prepared pan.

Step 4

Bake and cool. Bake for 50-60 minutes (for the loaf pan) or 40-50 minutes (for the square pan) until golden brown and a toothpick inserted into the center comes out clean.  Place on a wire rack.  Allow to cool for about 15 minutes in the pan.

Step 5

In a small bowl, combine the powdered sugar, lemon zest, and lemon juice for the glaze.  Pour over the still-warm cake.

Step 6

After the glaze has soaked in and hardened, remove cake from pan and allow to finish cooling on wire rack.  Slice and serve once cool.