Preheat the oven to 325° F.
Grease and line a 7" round cake pan or 8" loaf pan with parchment paper or wax paper.
Grate the lemon rinds and set aside.
Combine the juice of 1 lemon with 3 T. sugar in a bowl and set in a warm place until the sugar dissolves and forms a syrup with the lemon juice.
Cream the butter (or margarine) and the rest of the sugar together until light and fluffy.
Add the beaten eggs, a little at a time, beating well after each addition.
Stir in the grated lemon rind and flour; beat again thoroughly. (The longer you beat, the softer the cake.)
Add the milk and beat again.
Pour the batter into the prepared pan and bake for at least 1 hour; the cake should spring back when pressed gently in the center.
Immediately upon removing the cake from the oven, prick the top with a long-tined fork or thin skewer and pour the lemon-juice syrup all over the top until completely covered.
Cool in the pan to allow the syrup to be soaked up and create a moist and tangy cake.