01 - Preheat the oven to 350°F. Generously grease and flour a 10–12 cup bundt pan.
02 - In a medium bowl, whisk together flour, poppy seeds, baking powder, baking soda, and salt. Set aside.
03 - In a large bowl, beat the butter and sugar with an electric mixer until light and fluffy, about 3 to 4 minutes.
04 - Add eggs one at a time, beating well after each addition to ensure thorough incorporation.
05 - Mix in lemon zest, lemon juice, and vanilla extract until evenly combined.
06 - On low speed, gradually add the flour mixture in three parts, alternating with sour cream, beginning and ending with the flour mixture, mixing just until combined.
07 - Pour the batter into the prepared bundt pan and smooth the surface evenly.
08 - Bake for 45 to 50 minutes, or until a toothpick inserted into the center comes out clean.
09 - Allow the cake to cool in the pan for 15 minutes, then invert it onto a wire rack to cool completely.
10 - Whisk powdered sugar with enough lemon juice to achieve a thick but pourable consistency, then drizzle over the cooled cake.