Leave the butter outside the fridge, until it softens.
Beat the butter in the mixer with the paddle attachment at high speed for 1-2 minutes, until it gets fluffy.
Gradually add the sugar.
Stop the mixer, clear the sides and bottom of the bowl with a pastry spatula and continue in the same way, until the mixture becomes white enough and gets a light texture.
Add the eggs one by one, waiting each of them to be incorporated in the mixture, before we add the next one.
Use the mixer at low speed and add the flour gradually, in doses, waiting once again each dose to be incorporated, before we add the next one.
Do not beat the mixture excessively.
Add the zest and the vanilla and incorporate.
Transfer to a prepared pan and bake at preheat oven at 170°C for approximately 50 minutes.
The cake is ready, once you put a small knife inside and it comes out dry.
Remove from the oven and, after letting it cool for a while and turn out on to a rack, until it cools completely.
FOR THE GLAZE
Put all the ingredients in a bowl, apart from the granulated sugar, and whisk.
Add the granulated sugar in small doses and resume whisking, until all the ingredients are homogenized.
Pour the glaze on top of the cake and sprinkle with poppy seeds.
