Preheat oven to 350 F. Spray an 8-inch square cake pan with cooking spray or baking pans of your choice.
Whisk sour cream, white sugar, canola oil, eggs, 3 tablespoons limoncello, and lemon zest together in a large bowl.
Sift flour, baking powder, baking soda, and salt together in another bowl. Add flour mixture to sour cream mixture; stir with a wooden spoon until batter is just combined. Pour batter into prepared cake pan or pans.
Bake for about 35 minutes OR until a toothpick inserted into the center comes out clean. Cool cake(s) in the pan for 5 minutes.
Glaze
Whisk powdered sugar and 2 tablespoons limoncello liqueur together in a bowl until glaze is thin and smooth. Drizzle glaze over the top of the cake. Cool cake completely before serving. Top with a bit of whipped cream if desired.
Recipe Notes
You may need a bit more glaze if you have made individual cakes as I did here.