1. For the filling add milk, vanilla extract, poppy seeds, sugar, and semolina to a small saucepan. Heat up while stirring constantly. Let simmer until the mixture has thickened nicely. Remove from the heat and let cool down.

2. Preheat the oven to 350°F (180°C). Lightly grease a 10×5 inches (25x12cm) loaf pan and line with some baking paper. Set aside.

3. Mix the butter (or margarine), sugar, and vanilla extract in a large bowl until very light and fluffy. Add the eggs, one at a time, and mix well after each addition. Mix the flour with the baking powder, salt, and lemon zest. Add in two batches to the bowl, alternating with the buttermilk. Mix until just combined. Transfer the batter to the prepared loaf pan and smooth out the top.

4. Spoon the poppy seed filling onto the batter, then carefully mix with the batter to create some swirls. Bake the cake for about 60-65 minutes or until a wooden skewer inserted into the center of the cake comes out clean. Remove from the oven and let the cake cool down for several minutes before removing it from the pan by lifting it out with the baking parchment. Let cool down completely on a wire rack.

5. For the sugar glaze, mix the confectioners’ sugar with lemon juice and some heavy cream until smooth. The mixture should be quite thick. Add a bit more lemon juice or heavy cream, if necessary. Brush the cooled cake with the icing and let dry completely. Decorate the cake with some lemon slices to your liking (pat them dry first with some kitchen paper). Store leftovers in an airtight container at room temperature and eat the cake within 2-3 days.