1. Preheat the oven to 250 degrees F.
2. Grease 2, 8 x 4 loaf pans and keep aside.
3. In an electric mixer, cream the butter and sugar until light and fluffy.
4. Add in the egg yolks and lemon rind and beat until combined.
5. In another bowl, combine the all purpose flour with the baking powder and salt, mix well for the flour mixture.
6. Before blending the butter-sugar mixture in the electric mixer, add in 1/3 cup of the flour mixture with 1/2 cup of milk. Start the blender and alternately add 1/3 cup of flour with the rest of the milk. Finally add in the last cup of the flour and continue beating until well combined. Keep the batter aside.
7. In another bowl, beat 3 egg whites with a blender until stiff peaks are formed. Fold this egg white mixture into the batter gently.
8. Take the greased bread pans and scoop this batter into it and smooth out the surface with a spatula. Bake these pans in the preheated oven at 350 for about an hour or until done.
9. Once done, remove the pans and let them cool for 10 minutes. Remove the loaves from the pan and let them cool completely on the rack.
10. In another bowl add all the ingredients for the lemon glaze topping and beat until smooth.
11. Once the loaves are cooled, apply the lemon glaze over the top of the loaf and spread around evenly.
12. Slice the loaves into desired pieces and serve with tea or for breakfast.