The cake batter uses only 10 ingredients and comes together quickly.
Dry ingredients: Grab some all-purpose flour, baking powder, and salt. Simple!
Wet ingredients: You'll need room temperature unsalted butter. Then, some sugar, sourdough starter (either active sourdough starter or discard, both work fine), eggs, sour cream (this helps keep the crumb a bit lighter), vanilla extract, and some fresh lemons.