With the rack in the middle position, preheat the oven to 350°F (180°C). Butter a 9 x 5-inch (23 x 13 cm), 6-cup (1.5 litre) loaf pan and line with a strip of parchment paper, letting it hang over two sides. Butter and flour all sides of the parchment paper.
In a bowl, combine the flour, poppy seeds, baking powder and salt. Set aside.
In another bowl, combine the milk with the lemon zest and juice. Let sit for 5 minutes until the milk has curdled.
In a third bowl, cream the butter and sugar with an electric mixer until light and fluffy. While whisking, add the eggs one at a time until smooth. Add the dry ingredients alternating with the milk. Pour into the prepared loaf pan. Place the loaf pan on a baking sheet.
Bake for 1 hour 15 minutes or until a toothpick inserted in the centre of the cake comes out clean. Let cool completely on a wire rack before unmoulding.
Preheat the grill, setting the burners to medium-high. Oil the grate.
Lightly butter slices of cake and grill for 30 seconds on each side. Also delicious served with cherries jubilee and crème fraîche.