Cube the butter, add both flours, sugar and mix in a robot. Add lemon zest and mix again, add lemon juice from 1 lemon and mix again. Divide the dough into 24 pieces and form bowls and place on a baking sheet with 5cm spaces among them. With your thumb make hole in each bisquit and put lemon zest into them with a bit of sugar. Set the combi oven on hot air mode, 175°C for 8 minutes. After baking place the bisquits on a wire shelf.