First, sanitize the fish in case it is not already slaughtered: deep-freeze it with the function of shock freezing of Freddy until it reaches -18°C to the heart (help with a probe) and, subsequently, keep it in the freezer for at least 24 hours. In this way you will have completely sanitized your tuna and you can eat it raw in complete safety.
Wash the tomatoes, cut them in half, lay them on a baking tray, season with salt, sugar, pepper and oil and cook them in the preheated oven at 160ºC for about 50 minutes, then cool them quickly in Freddy with the function of blast chilling.
Cut the tuna (previously defrosted in case of felling) into small cubes in order to obtain a tartare and season with the grated rind of the lemon, salt, pepper and oil. Add the tomatoes to the tartare, give the classic cylindrical shape with the help of a pastry ring and serve with a spoonful of stracciatella.