For the pico de gallo: Combine the red onions, cilantro, salt, tomatoes and jalapenos in a bowl and toss to combine.
For the pork belly: Preheat the oven to 325 degrees F. Rub the pork belly with the 5-spice powder and salt and let rest at room temperature for 20 minutes.
Heat the canola oil in saute pan over medium-high heat. Brown the pork belly on all sides, and then transfer to an oven-safe dish. Pour in the beef broth, soy sauce, sugar and ginger, cover with foil and transfer to the oven to braise for 2 hours 30 minutes.
Remove from the oven and let cool in the liquid for 1 hour. Remove the pork belly from the liquid and cool in the refrigerator for 3 hours. Cut into 3- by 1-inch pieces
Assembly: Heat the olive oil in a large saute pan over medium-high heat. Add the pork belly and cook until crispy and heated through.
Place pieces of watermelon and pork belly in each tortilla and top with pico de gallo. Squeeze with fresh lime juice and a couple dashes of hot sauce.
NotesThis recipe was provided by a chef, restaurant or culinary professional and makes a large quantity. The Food Network Kitchens chefs have not tested this recipe, in the proportions indicated, and therefore, we cannot make any representation as to the results.