Clean the shrimps and make sure the intestine sac on their back is removed. Dice them finely and set them aside. Boil some slightly salty water in a large pot; pour the spaghettoni and allow to cook. In the meantime, let the butter melt with crushed pepper in a large pan and add a ladle of pasta cooking water. Drain the spaghettoni – which need to be al dente – and stir them in melted butter and pepper for a couple minutes. Turn off the stove and add pecorino, grana cheese and stir until creamy. Serve the dish by laying the prawn tartare on top of the spaghettoni.