01 - Preheat oven to 350°F. Generously grease and flour a bundt pan, ensuring all crevices are coated for easy release.
02 - Whisk together flour, poppy seeds, baking powder, baking soda, and salt in a medium bowl until thoroughly blended.
03 - Beat softened butter and granulated sugar with an electric mixer on medium-high speed for approximately 3 minutes until pale and fluffy.
04 - Add eggs one at a time, mixing well after each addition. Blend in lemon zest, lemon juice, and vanilla extract until combined.
05 - On low speed, alternate adding flour mixture and sour cream, beginning and ending with flour mixture. Add milk and mix just until combined—do not overmix.
06 - Transfer batter to prepared bundt pan, spreading evenly and smoothing the top with a spatula.
07 - Bake for 45-50 minutes until a wooden toothpick inserted into the center emerges clean or with just a few moist crumbs.
08 - Allow cake to rest in pan for 15 minutes before carefully inverting onto a wire rack. Cool completely before glazing.
09 - Whisk powdered sugar with lemon juice until smooth and pourable. Adjust consistency with additional juice if needed.
10 - Drizzle glaze over completely cooled cake, allowing it to cascade down the sides. Let set before slicing and serving.