Preheat oven to 350°F. Spray a 9- x 5-inch loaf pan with no-stick cooking spray then line with parchment paper, leaving a 2-inch overhang on all sides. Set aside.

In the bowl of a stand mixer fitted with a paddle attachment beat the granulated sugar and softened butter on medium speed until light and fluffy, about 2 to 3 minutes. Alternately, in a large bowl cream and butter and sugar using an electric mixer. Add the eggs, 1 at a time, beating well after each addition, about 2 minutes total. Be sure to stop the mixer and scrape down the sides and bottom of the bowl.

Mix in the vanilla extract, lemon zest and 2 tablespoons of the lemon juice until combined. In a medium bowl whisk together flour, poppy seeds, baking powder, baking soda, and salt.

Add the  flour mixture into sugar mixture in 3 additions, alternately with sour cream, beginning and ending with flour mixture.

Pour the batter into the prepared loaf pan, smooth the top with an offset spatula.

Bake in preheated oven until a wooden or metal skewer inserted in the center comes out with a few moist crumbs, 50 to 55 minutes. Remove the cake from oven, and let cool in loaf pan for 10 minutes. Remove the loaf from pan and let cool on a wire rack to room temperature.

In a small bowl, whisk together powdered sugar, milk, and remaining 1/2 tablespoon lemon juice until smooth.

Drizzle evenly over cooled loaf cake, cut and enjoy