01 - Preheat oven to 350°F. Thoroughly grease and flour a 10-cup Bundt pan.
02 - In a medium bowl, whisk together flour, poppy seeds, baking powder, baking soda, and salt. Set aside.
03 - Using an electric mixer, cream the butter and sugar in a large bowl until light and fluffy, approximately 3 to 4 minutes.
04 - Beat in eggs one at a time, mixing well after each addition. Stir in lemon zest and vanilla extract.
05 - Mix in fresh lemon juice and sour cream until just combined; the mixture may appear slightly curdled.
06 - Gradually fold dry ingredient mixture into the wet ingredients; mix until just incorporated to avoid overmixing.
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 onto a cooling rack to cool completely.
10 - Whisk powdered sugar, lemon juice, and lemon zest together until smooth and pourable.
11 - Drizzle glaze over cooled cake and let set for 10 minutes before slicing and serving.