01 - Preheat oven to 350°F. Thoroughly grease and flour a 10-cup Bundt pan, coating all crevices.
02 - In a medium bowl, whisk together flour, poppy seeds, baking powder, baking soda, and salt. Set aside.
03 - In a large bowl, beat butter and sugar with a mixer until pale and fluffy, about 3 to 4 minutes.
04 - Add eggs one at a time, beating well after each addition. Mix in lemon zest, lemon juice, and vanilla extract.
05 - Alternately add flour mixture and sour cream to wet ingredients, starting and ending with flour mixture. Mix just until combined to avoid overmixing.
06 - Pour batter evenly into prepared pan and smooth the surface. Bake for 40 to 45 minutes or until a toothpick inserted into the center comes out clean.
07 - Allow cake to cool in pan for 15 minutes, then invert onto a wire rack to cool completely.
08 - Whisk powdered sugar with 2 tablespoons lemon juice, adding more juice as needed for a pourable consistency. Drizzle glaze over cooled cake.
09 - Let the glaze set for 15 minutes before slicing and serving.