01 - Preheat your oven to 350°F. Grease and flour a 10-cup Bundt pan or a 9x5-inch loaf pan, ensuring all surfaces are coated to prevent sticking.
02 - In a medium bowl, whisk together the flour, poppy seeds, baking powder, baking soda, and salt until evenly distributed. Set aside for later use.
03 - Using an electric mixer or sturdy whisk, beat the softened butter and granulated sugar in a large bowl until the mixture becomes pale and fluffy, approximately 3 minutes.
04 - Add the eggs one at a time, beating thoroughly after each addition. Mix in the lemon zest, lemon juice, and vanilla extract until fully incorporated.
05 - Gradually add the dry ingredients to the wet mixture in three portions, alternating with the milk in two portions. Begin and end with the dry ingredients. Mix gently until just combined to avoid developing gluten.
06 - Pour the batter into the prepared pan and smooth the surface with a spatula. Bake for 45-50 minutes, or until a wooden toothpick inserted into the center emerges clean.
07 - Allow the cake to rest in the pan for 15 minutes before inverting it onto a wire rack. Let it cool completely to room temperature before glazing.
08 - Whisk the powdered sugar with enough lemon juice to achieve a thick but pourable consistency. Drizzle the glaze over the completely cooled cake just before serving.