Preheat oven to 350°F (175°C) and grease a loaf or bundt pan.

In a bowl, whisk together the flour, poppy seeds, baking powder, baking soda, and salt.

In another bowl, cream the softened butter and sugar together until light and fluffy.

Add eggs one at a time, beating well after each addition.

Stir in sour cream, lemon juice, lemon zest, and vanilla extract.

Gradually add the dry ingredients to the wet mixture, mixing until just combined.

Pour the batter into the prepared pan and smooth the top.

Bake for 45–50 minutes, or until a toothpick inserted into the center comes out clean.

Allow the cake to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.

Whisk together the powdered sugar, lemon juice, and milk to make the glaze. Drizzle over the cooled cake.