01 - Preheat oven to 350°F. Thoroughly grease and flour a 12-cup Bundt pan, ensuring all crevices are coated.
02 - In a medium bowl, whisk together flour, poppy seeds, baking powder, baking soda, and salt until evenly distributed.
03 - In a large bowl, beat softened butter and sugar with an electric mixer until light and fluffy, approximately 3 minutes.
04 - Add eggs one at a time, beating well after each addition. Mix in lemon zest, lemon juice, and vanilla extract until fully combined.
05 - In a separate bowl, whisk together milk and sour cream until smooth and well blended.
06 - With mixer on low speed, alternately add flour mixture and milk mixture to the butter mixture, beginning and ending with flour. Mix just until combined without overmixing.
07 - Pour batter evenly into the prepared Bundt pan and smooth the top with a rubber spatula.
08 - Bake for 45 to 55 minutes, or until a toothpick inserted into the center comes out clean.
09 - Cool cake in the pan for 15 minutes, then invert onto a wire rack to cool completely.
10 - Whisk powdered sugar, lemon juice, and zest until smooth and pourable. Drizzle over cooled cake and allow glaze to set before slicing.