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