Mix the basil, garlic, pine nuts, Parmigiano Reggiano, sea salt and pepper in a food processor. Slowly add the olive oil, until all the ingredients are mixed properly.
Cut the Duroc pork belly horizontally. Fill it with the homemade pesto. Tie it up like a roulade with some kitchen twine or butcher rope.
Let the meat cook slowly at the top of the spit for about 3.5 hours. Sprinkle regularly with fresh lemon juice.
Move the meat to the lower part of spit. Let it cook until the outside has become crispy and has turned to the desired colour.