Step 1

Add sugar, vanilla sugar, salt, lemon zest and butter to a bowl and use a dough hook to mix the sugar with the butter. Till the sugar is just incorporated.

Step 2

When the sugar and butter are incorporated (make sure not to over mix it), lightly whisk the egg and add about 2/3 of the egg to the butter and add all of the flour. Mix until a dough starts to form.

Step 3

Once the dough is formed, take it out of the bowl and if needed, lightly knead it on a floured work surface. The dough will be very soft, so don't knead too much, usually 30 seconds to form the dough and check if everything is incorporated is enough.

Step 4

Take the dough and wrap it in clingfilm. Flatten the dough to help it cool faster. Leave the dough in the fridge for at least 30 minutes.

Step 5

Preheat the oven to 350°F/175°C. Grease a butter cake pan. If you don't have a butter cake pan, grease and line a brownie pan or spring form with baking paper.

Step 6

Press the dough into your cake pan. If needed put a piece of baking paper on top of the dough to smooth out the dough more easily.

Step 7

Take a fork and run the back of the fork on the dough to create a pattern. Use the remaining egg to brush the top of the butter cake.

Step 8

Bake in the oven for 20-25 minutes, till golden.

Step 9

Leave to cool completely. To serve, cut small triangle pieces or little cubes.