Preheat the oven to 350 F.

Grease a 10-inch tube-type pan and dust the pan with flour.

In a small bowl, combine the poppy seeds and milk.

Cover and refrigerate overnight.

In a large bowl, cream the butter, lemon zest, and sugar until creamy.

Add the egg whites and beat at high speed with an electric mixer until the mixture is light and fluffy.

Place the cake flour, baking powder, and salt into a sieve and set it over the bowl.

With a spoon, stir the mixture until it is sifted into the creamed mixture.

Add the poppy seed-milk mixture and with an electric mixer at MEDIUM speed beat until the batter is light and fluffy, scraping the sides of the bowl often.

Pour the batter into the prepared pan and bake for 45 to 55 minutes or until a wooden skewer inserted in the centre comes out clean.

Let the cake cool in the pan for 5 minutes, then invert it out onto a wire rack to finish cooling completely.

To make the glaze, in a small bowl, stir together the confectioners' sugar, butter, and lemon juice until smooth.

Drizzle the icing over the cooled cake.

Slice and serve.