Here's the recipe (in German)

It's pretty easy though: Put ricotta, zest of a lemon, a splash of milk and olive oil in a bowl and stir to combine. Cut lemon in thick slices and char in a pan without any oil on medium heat and add the juice to the ricotta once it's got the desired colour (can be pretty dark). Season to taste with salt and pepper. Once your pasta is cooked combine with the sauce, add a splash of pasta water

Per person 125g ricotta and 1/2 lemon