Cook the tagliatelle in boiling salted water until al dente, drain in a colander and leave to drain. In the meantime, lightly toast the hazelnuts in a pan without fat and then put them in a bowl. Add the breadcrumbs, grated lemon zest, cinnamon, sugar and cocoa and mix everything well. Add the tagliatelle to the bowl. Heat the butter a little and add it. Mix the ingredients together.
Grease an ovenproof baking dish with butter, add the tagliatelle-nut mixture and bake in a preheated oven at 200 degrees for about 5 minutes.