Preheat your oven to 180°C (350°F). Grease a 23cm (9-inch) loaf tin and line it with parchment paper for easy removal.
In a large mixing bowl, whisk together the flour, baking powder, and a pinch of salt. Set this dry mixture aside.
In another bowl, beat the softened butter and caster sugar together with a whisk or an electric mixer until the mixture is pale, fluffy, and fragrant, about 3-4 minutes. You should see the color lighten and the texture become airy.
Add the eggs one at a time, beating well after each addition to ensure a smooth, cohesive batter. Stir in the lemon zest and lemon juice, which will fill your kitchen with a bright citrus aroma.
Gradually fold the dry ingredients into the wet mixture, mixing gently just until combined. If using, fold in the poppy seeds for a subtle crunch and visual appeal.
Pour the batter into your prepared loaf tin, smoothing the top with a spatula to ensure an even surface.
Bake in the preheated oven for about 45-50 minutes, or until the cake turns a lovely golden brown and a skewer inserted into the center comes out clean. Keep an eye on it towards the end to prevent over-browning.
While the cake bakes, prepare the lemon glaze by mixing the icing sugar with 2-3 tablespoons of lemon juice until you achieve a smooth, glossy consistency. It should be pourable but not runny.
Once baked, remove the cake from the oven and let it cool in the tin for about 10 minutes. Then transfer it to a wire rack to cool completely, which helps set the texture and prevents sogginess.
Prick the cooled cake all over with a skewer or toothpick, then evenly drizzle the lemon glaze over the top. Allow the glaze to soak in and set for at least 30 minutes before slicing.
Slice the cake and serve as a bright, citrusy treat. Enjoy it with tea or fresh fruit, and revel in the sunny aroma and tender crumb.
