01 - Preheat oven to 350°F. Generously grease and flour a 10-12 cup Bundt pan, ensuring all crevices are coated for easy release.
02 - In medium bowl, whisk together flour, poppy seeds, baking powder, baking soda, and salt until evenly distributed. Set aside.
03 - Beat butter and granulated sugar with electric mixer on medium-high speed until pale and fluffy, approximately 3-4 minutes. Scrape bowl as needed.
04 - Add eggs one at a time, beating thoroughly after each addition. Blend in lemon zest, lemon juice, and vanilla extract until fully incorporated.
05 - On low speed, add flour mixture and sour cream in alternating batches, starting and ending with flour mixture. Mix only until just combined to prevent tough texture.
06 - Transfer batter to prepared Bundt pan, spreading evenly. Bake 45-50 minutes until wooden pick inserted in center emerges clean.
07 - Let cake rest in pan 15 minutes, then invert onto wire rack. Cool completely before glazing to prevent runoff.
08 - Whisk powdered sugar, lemon juice, and zest until smooth and pourable. Drizzle over cooled cake and allow to set before serving.