Preheat the oven to 350°F (180°C) and prepare the loaf pan.
Whisk together flour, poppy seeds, and baking powder in a bowl.
Cream butter, sugar, and zest in another bowl, then add eggs and beat until smooth.
Stir in dry ingredients alternately with lemon juice and milk.
Transfer batter to the prepared pan and bake for 1 hour.
Let the loaf cool completely before unmoulding.
Prepare the glaze by whisking together icing sugar and lemon juice until smooth.
Drizzle the glaze over the cooled lemon poppy seed loaf on a serving platter.
