01 - Preheat oven to 350°F. Generously grease and flour a 10 to 12 cup bundt pan, ensuring all crevices are coated.
02 - In a medium bowl, whisk together flour, poppy seeds, baking powder, baking soda, and salt. Set aside.
03 - In a large bowl or stand mixer, cream butter and sugar together on medium speed until light and fluffy, approximately 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 until fully combined.
05 - Add the flour mixture in three parts, alternating with buttermilk, beginning and ending with flour. Mix until just incorporated; avoid overmixing.
06 - Pour batter evenly into the prepared bundt pan. Smooth the top with a spatula to ensure even baking.
07 - Bake for 45 to 55 minutes, or until a toothpick inserted in the center comes out clean.
08 - Let the cake cool in the pan for 15 minutes, then carefully invert onto a wire rack to cool completely.
09 - Whisk powdered sugar with 2 tablespoons lemon juice and zest until smooth and pourable. Add additional lemon juice as needed to achieve desired consistency.
10 - Drizzle the glaze over the cooled cake. Allow it to set before slicing and serving.