Rub the salt, pepper and allspice into the oxtails. Wrap with cling wrap and refrigerate 2 hours, up to overnight.
Heat 4 tablespoons oil in a Dutch oven over medium heat.
Lightly dust spice-rubbed oxtails with flour and sear in batches until well browned on all sides, about 10 minutes per batch. (Do not overcrowd pan to prevent steaming.) Place on paper towels to drain.
Scrape sides and bottom of pot to release burnt pieces (these will add good flavor.)
Add ancho chilies to same pot and fry 2 minutes, adding oil as needed.
Stir in onions, garlic, garlic chili sauce, fish sauce and cayenne and cook until onions begin to soften, about 5 minutes.
Add chicken stock and bring to a boil over high heat. Turn off heat, cover and let sit 15 minutes.
Puree sauce mixture in batches. Strain through a fine sieve.
Return sauce to pot and bring to a boil over high heat. Add reserved oxtails, reduce heat to a slow simmer. Cover and cook for 1 hour 30 minutes.
Gently stir in cannellini beans and cherries. Cover and cook 30 minutes. Serve with gremolata (recipe below).
30 minutes before oxtails are ready, add all the gremolata ingredients in a bowl and mix until fully combined. Cover with cling wrap and refrigerate until ready to serve.