01 - Preheat the oven to 350°F. Grease and flour a 10-12 cup bundt pan thoroughly, ensuring all crevices are coated to prevent sticking.
02 - In a medium bowl, whisk together flour, baking powder, baking soda, salt, and poppy seeds until well blended. Set aside for later use.
03 - In a large bowl, beat softened butter and granulated sugar with an electric mixer on medium-high speed until light and fluffy, approximately 3 minutes. The mixture should appear pale in color.
04 - Add eggs one at a time, beating thoroughly after each addition. Incorporate lemon juice, lemon zest, and vanilla extract, mixing until fully combined.
05 - With mixer on low speed, add flour mixture in three additions, alternating with sour cream and milk. Begin and end with flour mixture. Mix only until just incorporated; avoid overmixing to prevent tough texture.
06 - Spoon batter evenly into prepared bundt pan, smoothing the top surface with a spatula. Tap pan gently on counter to release air bubbles.
07 - Bake for 45-50 minutes or until a wooden skewer inserted into the center emerges clean. The cake should be golden brown and pulling slightly from pan edges.
08 - Allow cake to cool in pan for 15 minutes. Carefully invert onto wire rack to cool completely before glazing.
09 - Whisk together sifted powdered sugar, lemon juice, and lemon zest until smooth and pourable. Adjust lemon juice quantity to achieve desired consistency.
10 - Drizzle prepared glaze evenly over cooled cake, allowing it to cascade down sides. Let glaze set completely before slicing and serving.