01 - Preheat the oven to 350°F. Grease and flour a bundt pan thoroughly, ensuring all crevices are coated to prevent sticking.
02 - In a medium bowl, whisk together flour, poppy seeds, baking powder, baking soda, and salt until well blended. Set aside.
03 - In a large bowl, beat the butter and sugar with an electric mixer on medium-high speed until light and fluffy, approximately 3 minutes.
04 - Add eggs one at a time, beating well after each addition until fully incorporated. Mix in lemon zest, lemon juice, and vanilla extract until combined.
05 - On low speed, alternately add the flour mixture and sour cream to the wet ingredients, beginning and ending with flour mixture in three additions. Add milk and mix until just combined, being careful not to overmix.
06 - Pour the batter into the prepared bundt pan, spreading evenly and smoothing the top with a spatula.
07 - Bake for 45–50 minutes, or until a wooden toothpick inserted into the center comes out clean or with just a few moist crumbs.
08 - Let the cake cool in the pan for 15 minutes, then carefully invert onto a wire rack and allow to cool completely before glazing.
09 - Whisk powdered sugar with lemon juice until smooth and pourable, adding more juice if needed to achieve desired consistency. Drizzle evenly over the cooled cake.