First, dry the pork meat with paper towel. Then, mix the soy sauce, wine, sugar, garlic, cinnamon, cloves and orange zest in a bowl and pour into a rectangular mold large enough to fit the meat.
Place the pork belly in the container, making sure that only the meat is in contact with the marinade and the skin is completely dry. Refrigerate for at least 8 hours (ideally overnight).
Preheat the oven to 180°C. Place the pork belly on the oven grid and, under the meat, put the same mold in which it was marinated. This way, as the pork belly cooks, the fat will drain into the mold and the marinade will reduce, making a condensed and very tasty broth. Add one cup of salt evenly over the skin of the pork and let it bake for about 40 minutes.
Then, remove the pork and broth, and raise the oven temperature to 240°C. The salt should have formed a crust; remove it by scraping it with a knife. Once the oven has reached the desired temperature, put the pork belly in the oven to cook again (without the mold with the broth) for about 30 minutes, until the skin is bubbly and crisp. Remove the meat from the oven and let it cool a few minutes before cutting.
For the puree, cook the sweet potatoes, apple and banana in a covered pot. Add the orange juice and anise. Once ready, remove the star anise and crush everything, adding very cold butter.
Finally, serve the pork belly with the puree on the side.