01 - Preheat oven to 350°F. Grease and flour a 10-12 cup bundt pan thoroughly, ensuring all crevices are coated.
02 - Whisk together flour, baking powder, baking soda, salt, and poppy seeds in a medium bowl until well combined.
03 - Beat softened butter and granulated sugar on medium-high speed until light and fluffy, approximately 3 minutes.
04 - Add eggs one at a time, beating thoroughly after each addition. Mix in lemon juice, lemon zest, and vanilla extract.
05 - On low speed, add flour mixture in three additions, alternating with sour cream and milk. Begin and end with flour, mixing only until just combined.
06 - Spoon batter evenly into prepared bundt pan and smooth top. Bake for 45-50 minutes until a skewer inserted into center comes out clean.
07 - Let cake cool in pan for 15 minutes, then carefully invert onto wire rack to cool completely.
08 - Whisk together powdered sugar, lemon juice, and lemon zest until smooth and pourable. Adjust juice quantity to achieve desired consistency.
09 - Drizzle glaze evenly over cooled cake. Allow glaze to set before slicing and serving.