1 (8 by 4 by 2 1/2-inch) loaf pan - or any 6-cup loaf or fluted tube pan, sprayed with non-stick vegetable spray or greased and floured. Line bottom with parchment paper and spray or grease and flour again
Preheat oven to 350 degrees.
In a medium bowl, lightly combine the milk, eggs and vanilla. In a large mixing bowl, preferably with the whisk beater, combine the flour, sugar, baking powder, salt, lemon zest and poppy seeds. Mix on low speed for 30 seconds to blend. Add the butter and half the egg mixture. Mix on low speed until the dry ingredients are moistened. Increase to medium speed (high speed if using a hand held mixer) and beat for 1 minute to aerate and develop the cake's structure. Scrape down the sides of the bowl. Gradually add the remaining egg mixture in 2 batches, beating for 20 seconds after each addition to incorporate the ingredients and strengthen the structure. Scrape down the sides. Scrape the batter into the prepared pan and smooth the surface with a spatula. The batter will be almost a 1/2-inch from the top of the 4-cup loaf pan. Bake 55 to 65 minutes at 350 degrees (35 to 45 minutes in a fluted tube pan) or until a wooden toothpick inserted in the center comes out clean. Be sure to use a wooden toothpick to test for doneness. (The cake will spring back when pressed lightly in the center even before it is done. If the cake is under baked, it will have tough, gummy spots instead of a fine, tender crumb.) Cover loosely with buttered foil after 30 minutes to prevent over browning. The cake should start to shrink from the sides of the pan only after removal from the oven. To get an attractive split down the middle of the crust, wait until the natural split is about to develop (about 20 minutes) and then with a lightly greased sharp knife or single-edged razor blade make a shallow mark about 6 inches long down the middle of the cake. This must be done quickly so that the oven door does not remain open very long or the cake will fall. When the cake splits, it will open along the mark.
Shortly before the cake is done, prepare the Lemon Syrup: In a small pan over medium heat, stir the sugar and lemon juice until dissolved. As soon as the cake comes out of the oven, place the pan on a rack, poke the cake all over with a wire tester and brush it with 1/2 the syrup. Cool in the pan for 10 minutes. Loosen the sides with a spatula and invert onto a greased wire rack. Poke the bottom of the cake with a wire tester, brush it with some syrup and reinvert onto a greased wire rack. Brush the sides with the remaining syrup and allow to cool before wrapping airtight. Store 24 hours before eating to give the syrup a chance to distribute evenly.
Slice with a thin sharp knife into thin slices. Serve with Fresh Blueberry Glaze and lightly whipped cream.
Fresh Blueberry Glaze:
Rinse the berries and allow them to dry thoroughly on paper towels. Place the berries in a bowl. In a medium saucepan, stir together the arrowroot and sugar. Stir in the water and lemon juice and heat, stirring constantly, until the mixture is clear and thickened. With arrowroot this will happen before the boil. Remove the pan from the heat and add the blueberries all at once, tossing until coated with the glaze. The berries will turn a bright blue. Empty the berries into a colander or strainer to drain away any excess glaze not clinging to berries.