Preheat the oven to 350 F and grease TWO regular sized loaf pans OR a bundt pan with nonstick cooking spray.
In medium bowl, beat butter and sugar until light and fluffy.
Add the lemon zest, lemon extract, and eggs. Beat until well combined.
Add the lemon juice and sour cream. Mix until combined.
In a separate bowl, whisk together the flour, cornstarch, baking powder, and salt.
Add half the dry ingredients to the butter mixture and mix until combined.
Pour the milk into the bowl and mix.
Add the remaining flour and mix until combined.
Pour the batter into the prepared pan(s) and bake for 45 to 55 minutes or until a toothpick inserted into the center comes out clean.
Allow the cake(s) to cool in the pan(s) for 10 to 15 minutes, then remove it from the pan(s) and place them on a wire cooling rack to cool completely.
While the cake(s) are cooling, make the glaze by mixing the powdered sugar, lemon extract, and two tablespoons of milk. Whisk until smooth. Continue adding milk one tablespoon at a time until desired consistency is reached.
When the cake(s) have cooled, drizzle the glaze over the top. Allow the cake(s) to rest for 10 minutes to allow the glaze to set before serving.
Notes
This recipe makes either two regular sized loaves or one bundt cake.