Preheat the oven to 350°. Butter a 9-inch round cake pan and dust with the bread crumbs; tap out any excess crumbs. In a medium bowl, whisk the all-purpose flour and cake flour with the baking powder and salt. In a large bowl, using a handheld electric mixer, beat the butter with the granulated sugar at medium-high speed until it is pale and fluffy. Beat in the eggs, 1 at a time, beating well between additions. At low speed, in 2 alternating batches, beat in the dry ingredients and the milk. With a rubber spatula, fold in the lemon zest, lemon extract and poppy seeds.
Using a rubber spatula, scrape the batter into the prepared pan and bake for 30 minutes, until a cake tester inserted in the center of the cake comes out clean.
Carefully invert the cake onto a wire rack and let cool to room temperature. Transfer the cake to a serving plate.
In a medium bowl, stir the confectioners' sugar with the lemon juice to make a runny glaze. Using a spatula, spread the glaze over the cake, letting it run down the sides. Cut into wedges and serve.
The cake can be stored in an airtight container for 2 days.