Put chocolate and butter in a pot and melt it on low heat. Stir and make sure it doesn’t start to boil. When it is melted, add in sugar and check that the mixture is not too hot (wait and cool it down if it is), because now you need to whisk in eggs, one by one.
Put flour, salt and cocoa powder in a bowl and stir then add it to the chocolate mixture while whisking.Leave just a few spoons of batter for topping but pour the rest of it in a baking tray with baking paper and spread it a little. I used baking tray size 36x21,5 cm.
Now prepare the cheesecake batter by simply adding all the ingredients (cream cheese, egg, little vanilla aroma, sugar, lemon juice and zest) in a bowl and mix until smooth. Put in on top of the brownie base and spread with a spoon equally. Add remained brownie batter on top with a spoon and draw swirl lines from it with a toothpick.
Bake it in a preheated oven on 180 degrees Celsius for about 30 - 35 minutes. Take it out of the oven and leave to cool down completely, then slice and serve.