01 - Preheat the oven to 350°F (175°C). Generously grease and flour a 10–12-cup Bundt pan, ensuring all crevices are coated.
02 - Whisk together the flour, baking powder, baking soda, salt, and poppy seeds in a medium bowl. Set aside.
03 - Beat the softened butter and granulated sugar on medium speed until light and fluffy, about 3 to 4 minutes.
04 - Add eggs one at a time, beating well after each addition. Stir in lemon zest and vanilla extract.
05 - In a measuring cup, mix fresh lemon juice and whole milk.
06 - With the mixer on low, alternate adding the flour mixture and the milk-lemon juice mixture to the batter, beginning and ending with the flour. Mix until just combined without overmixing.
07 - Pour batter evenly into the prepared pan and smooth the surface with a spatula.
08 - Bake for 45 to 55 minutes or until a skewer inserted into the center comes out clean.
09 - Let the cake cool in the pan for 15 minutes, then invert onto a wire rack to cool completely.
10 - Whisk powdered sugar, lemon juice, and lemon zest until smooth and pourable. Drizzle over the cooled cake and allow to set before slicing.