Finely grate the peel from ONE lemon, and squeeze out the juice from ONE lemon; set aside.
With an electric mixer beat the butter, 1-1/2 cups sugar, and the lemon extract (if using) until light and fluffy for about 4-5 minutes (no less than 4 minutes, no sugar granules should remain in the creamed mixture!).
Crack eggs open in a dish, making certain that there are no shells.
Add in a couple at a time to the creamed mixture, beating well after each addition(beat until fluffy, about 3 minutes).
In a small bowl, mix the flour with baking powder.
Add in 1 cup at a time to the creamed mixture; beat until well combined.
Stir in chopped walnuts.
Transfer the batter to prepared cake pan.
Bake for 40 minutes, or until cake tests done.
While the cake is baking, prepare the syrup.
Combine remaining 2 cups sugar with 2 cups water.
Slice remaining lemon into wedges.
Squeeze out the juice into sugar/water, the drop in a couple wedges.
Bring to a boil; boil 5 minutes.
Remove lemon wedges.
When cake has finished baking, pour the hot lemon syrup over warm cake.