In a mixing bowl, cream the butter, then add eggs and sugar. Stir to combine. Next, add flour, baking powder, baking soda, salt, milk, lemon juice, and lemon extract. Stir until mixed. Add lemon zest, and stir only until mixture is combined.
Preheat your oven to 350°F
Spray your baking dish with cooking spray, then pour your batter into the baking dish. Smooth out the batter, then place it into the oven and bake for 30 to 45 minutes (depending upon your oven), or until a toothpick inserted into the center of your cake comes out clean. Once your cake is baked, remove it from the oven and allow it to cool.
While your cake is cooling, mix together 2 ½ cups of powdered sugar, and 3 tablespoons lemon juice. Your frosting should be kind of thick. Set aside until your cake has cooled.
After your cake has cooled close to room temperature, add your frosting on top of the cake, then zest your lemon to top the cake. Serve right away, or store in the fridge until you were ready to serve. Serve and enjoy!