Cream 250 g unsalted butter, softened, 225 g dark brown sugar and 1 tablespoon lemon zest until light and fluffy, about 4–5 minutes.
Add 4 large eggs, one at a time, beating well after each addition to keep the batter smooth.
Sift together 225 g self-raising flour, 1½ teaspoons baking powder, and ¼ teaspoon salt, then mix into the batter until just combined.
Stir in 2 tablespoons lemon juice, 1 teaspoon vanilla paste, and 2 tablespoons whole milk until the batter is smooth and evenly combined.
Pour the batter into the prepared pan and smooth the top. Bake for 40–45 minutes, until golden and a toothpick inserted into the cake comes out clean.
Mix 100 g granulated sugar with 150 ml lemon juice until the sugar dissolves.
While the cake is still warm, make small holes and brush the cake with the lemon syrup so it soaks in fully.
Let the cake cool completely in the pan, allowing about 2 hours, then transfer it to a serving plate.
Make a few more holes, brush again with the remaining syrup, then whisk 80 g powdered sugar with 2 tablespoons water and drizzle over the cooled cake.
Slice and serve.
Notes
Flour choice: Use self-raising flour together with the listed baking powder and salt; plain all-purpose flour is not a direct substitute in this recipe.Pan size: This recipe was baked in a 20 cm silicone Bundt pan. A different size or material may change the baking time.Storage: Keep the cooled cake in an airtight container in the refrigerator for up to 3 days. Let individual slices come to room temperature before serving.