01 - Preheat oven to 350°F. Grease and flour a 9-inch round cake pan or line it with parchment paper.
02 - Whisk together the flour, poppy seeds, baking powder, and salt in a medium bowl. Set aside.
03 - In a large bowl, beat the softened butter and granulated sugar until light and fluffy, about 3 minutes.
04 - Add eggs one at a time, beating well after each addition. Stir in vanilla extract and lemon zest.
05 - Mix in half of the dry ingredients, then add milk and lemon juice. Fold in remaining dry ingredients gently until just combined to avoid overmixing.
06 - Pour the batter into the prepared pan and smooth the surface evenly.
07 - Bake for 40 to 45 minutes or until a toothpick inserted into the center comes out clean.
08 - Allow the cake to cool in the pan for 10 minutes before transferring to a wire rack to cool completely. Slice and serve.