Instructions

1. Peel 1 head garlic cloves (8 to 10 cloves). Place the cloves in a mortar and pestle with a pinch of kosher salt and mash until a paste forms. Transfer to a large bowl. Add 2 tablespoons soy sauce, 1 tablespoon lime juice, 1 tablespoon sazón con achiote, 1 tablespoon kosher salt, 1 1/2 teaspoons dried oregano, and 1 teaspoon black pepper. Stir to combine. (Alternatively, process the garlic cloves with all the seasonings together in a mini food processor or blender until a paste forms, then transfer to a large bowl.)
2. Add 3 to 4 pounds oxtails and toss until well-coated. Let marinate for at least 1 hour at room temperature, or cover and refrigerate overnight.
3. Heat 1 1/2 tablespoons canola oil in a stainless steel Dutch oven or heavy-bottomed pot (not enamel-coated) over medium-high heat until shimmering. Add 1/2 teaspoon granulated sugar and cook until the sugar is dark brown, about 2 minutes.
4. Working in 2 batches so as to not crowd the pot, add the oxtails with tongs (reserve the marinade left in the bowl), shaking off as much garlic as possible back into the bowl. Cook until browned on all sides, 8 to 9 minutes. Transfer to a plate. When all the oxtails are browned, return them to the pot.
5. Add the reserved marinade and enough water so the oxtails are fully submerged. Bring to a boil. Reduce the heat to maintain a simmer and partially cover with a lid. Cook, stirring occasionally, until the oxtails are tender, about 2 hours. If the liquid reduces to about 1/3 and the oxtails are still tough, add 1 cup water.
6. Meanwhile, prepare the following, adding each to a medium bowl as you complete it: Cut 1 medium white or red onion, 1/2 medium green bell pepper, and 1/2 medium red bell pepper into 1/4-inch-thick slices; add 1 teaspoon red white or distilled white vinegar; and toss to combine. Let sit until the oxtails are ready.
7. When the oxtails are tender, uncover and cook until the liquid is reduced to about 1/3 of the original amount, slightly thickened, and darkened in color, about 30 minutes, skimming off fat from the surface if desired. Meanwhile, finely chop until you have 2 tablespoons fresh cilantro leaves and tender stems.
8. Add the cilantro and 1 tablespoon tomato paste to the pot and stir until the tomato paste is completely dissolved. Stir in 1 whole hot pepper; leaving it whole will result in a mildly spicy oxtail stew, or you can dice it first for a spicier stew. Simmer until the sauce is thickened, about 10 minutes more.
9. Add the onions and bell peppers, and stir to combine. Remove the pot from the heat and let rest for 5 to 10 minutes. Serve with rice and plantains if desired.