Preheat oven to 350 degrees F (175 degrees C). Spray an 8-inch square cake pan with cooking spray.
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.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, 33 to 35 minutes. Cool cake in the pan for 5 minutes.
Whisk confectioners' sugar and 2 tablespoons limoncello liqueur together in a bowl until glaze is thin and smooth. Spread glaze over the top of the cake. Cool cake completely before slicing.