Line four 9-inch round pans with parchment paper. Preheat oven to 350°F (175 degrees C).
Measure sifted flour, baking powder, and salt: sift together.
Cream butter and lemon zest together in the bowl of a stand mixer or hand-held mixer for about 3 minutes.
Gradually add sugar, creaming until light and fluffy.
Add eggs one at a time, beating thoroughly after each addition.
Add lemon extract to the milk and stir.
Add sifted ingredients alternately with milk to the creamed mixture, a small amount at a time; gently mix after each addition until smooth.
Bake for 25 to 30 minutes or until an inserted toothpick is removed clean.
Cool on wire racks.