Dip tomatoes in boiling water for some seconds, drain and pass them in water with ice. Peel and remove the seeds. Cook tomatoes with sugar, the vanilla pod and the lemon zest for approximately 45 minutes on a low flame to obtain a jam. Sear rocket in boiling water and dip in water with ice to fix its colour. Drain and place in a container with pine nuts, oil and grated pecorino romano cheese. Blend until you obtain smooth pesto. Cook Stelle Bufala, drain and season with extra virgin olive oil. Place in a dish and finish with drops of pesto and petals of jam.