In a small bowl, mix 120 g of powdered sugar with 30 g of limoncello until smooth. The consistency should be thick but runny enough to glaze the cake, similar to corn syrup, to give you an idea.
For the loaf:
Preheat the oven to 350°.
In a medium bowl, sift 265 g of cake flour, 4 g of baking powder and 4 g of baking soda, add 25 g of poppy seeds, and set it aside.
In a stand mixer bowl, pour 150 g of room temperature butter and 115 g of mascarpone, and 280 g of granulated sugar.
Start beating until nice and fluffy, then add three room temperature eggs one at a time, the zest of two lemons, and 25 g of limoncello.
Mix for another minute, then add the sifted flour and baking soda one spoonful at a time.
Once all the flour is incorporated, transfer the batter into a greased 8x5 loaf pan and bake at 350° F for 60 minutes or until the cake's center reaches 200° F.
Remove the cake from the oven and let cool for 20 minutes before removing it from the pan.
When the cake is cool, place it on a cooling rack and pour the glaze on top. Using a small spatula, spread the glaze evenly all over the surface, then sprinkle with some poppy seeds.
Notes
How to store limoncello pound cake:
You can keep this cake wrapped in plastic at room temperature for three days or up to 5 days in the fridge. You can also freeze it for up to 2 months. To defrost it, leave it on the counter overnight.