01 - Preheat oven to 350°F. Grease and flour a 10-12 cup Bundt pan thoroughly, tapping out excess flour.
02 - Whisk together flour, baking powder, baking soda, salt, and poppy seeds in a medium bowl. Set aside.
03 - Using an electric mixer, cream butter and sugar until light and fluffy, approximately 3 minutes.
04 - Beat in eggs one at a time, mixing well after each addition. Scrape down bowl sides as needed.
05 - Mix in lemon juice, lemon zest, and vanilla extract until just combined.
06 - On low speed, alternately add flour mixture and milk in three additions, beginning and ending with flour. Mix until just combined without overmixing.
07 - Gently fold sour cream into batter until smooth and evenly distributed.
08 - Pour batter evenly into prepared Bundt pan. Smooth top with spatula.
09 - Bake in center of oven for 45-55 minutes until skewer inserted in center comes out clean.
10 - Let cake cool in pan for 15 minutes, then carefully invert onto wire rack to cool completely.
11 - Whisk powdered sugar, lemon juice, and lemon zest until smooth and pourable. Drizzle over cooled cake before serving.