Prepare and preheat your sous vide machine to 150° F.
Blend the onion, ginger, soy sauce, vinegar, zest, and orange juice in a blender or food processor until smooth.
Place the marande and pork belly into a sous vide, vacuum, or zip-loc freezer baggie and remove as much as air possible.
Place in the sous vide machine and cook for 20-24 hours.
Remove the belly from the sous vide machine.
Remove the bell from the bag and reserve the juices and marande.
Place the marande and juices in a sauce pot and reduce by half (or more if you want it more intense and thick) to make a sauce.
Remove the skin of the pork belly with a knife (optional)
Heat a pan or cast iron skillet over medium-high heat and add a tablespoon of vegetable oil or other high temperature fat.
Sear the fat side (or skin side if you left the skin on) until golden brown.
Plate the pork belly and either drizzle with the belly with the marinade sauce or service on the side.
You can sous vide at a higher temperature, but consider going with a lower cooking time. Cooking with a temperature around 175° F will reduce the cooking time to around 8 hours.Feel free to experiment with the sauce and maranade ingredients. This is just a recommendation and I find the salt from the source sauce and the orange flavor goes well with how fatty this cut is. Sriracha would be an excellent addition