01 - Preheat oven to 350°F (175°C). Grease and flour a 9x5-inch loaf pan or line it with parchment paper.
02 - In a large bowl, beat the softened butter and granulated sugar together until pale, light, and fluffy.
03 - Add eggs one at a time, beating well after each addition until fully incorporated.
04 - Stir in the whole milk, fresh lemon juice, and lemon zest until combined. The batter may appear slightly curdled — this is normal.
05 - In a separate bowl, whisk together the all-purpose flour, baking powder, salt, and poppy seeds until evenly distributed.
06 - Gradually add the dry ingredient mixture to the wet batter, folding gently with a spatula until just incorporated. Do not overmix.
07 - Pour the batter into the prepared loaf pan and smooth the top with a spatula for an even surface.
08 - Bake for 35 to 40 minutes, or until a toothpick inserted into the center of the cake comes out clean.
09 - Let the cake cool in the pan for 10 minutes, then carefully transfer it to a wire rack to cool completely.
10 - Whisk together the powdered sugar and fresh lemon juice until smooth. Drizzle the glaze evenly over the completely cooled cake before slicing and serving.