For the rice: Heat 6 cups broth and the coconut milk in a medium saucepan just until steaming. I don't usually heat the liquid before adding it to the rice, but if cooked too long, coconut milk can scorch and give the rice an off flavor. Heating the coconut-broth mixture beforehand means the liquid will come to a boil faster and cook down faster, lessening the chance of burning the coconut milk.
Heat the achiote oil in a 4 to 5-quart heavy pot or dutch over medium heat. Add the sofrito and cook, stirring, until the liquid is evaporated and the sofrito is sizzling. Stir in the alcaparrado, chile, and salt and stir for a minute or two. Add the rice and stir until it is coated with seasoned oil and the grains start to turn chalky. Increase the heat to medium-high and pour in the heated coconut milk and broth. If there isn't enough liquid to cover the rice by the width of two fingers, add more as needed. Bring the liquid to a boil. Boil (without stirring!) until the liquid is boiled down to the level of the rice.
Reduce the heat to very low, cover the pot and cook — without lifting the lid or, God forbid, stirring — until the liquid is absorbed and the rice is tender, about 20 minutes. The rice can be held in a warm corner of the stove with the lid on for up to 45 minutes. Serve very hot or warm.
For pork ribs: Cut the spareribs into single serving size pieces if necessary. Pat the ribs dry with paper towels and put them in a large bowl. Rub the achiote oil into all sides of the ribs with your hands, then sprinkle the vinegar over them and toss to mix. Season liberally with adobo, rubbing the seasoning into the pork and making sure all sides of the ribs are well seasoned. Let them stand at room temperature for an hour or cover and refrigerate for up to 2 days. (Hint: 2 days is better!)
Preheat the oven to 400 degrees F. Heat the olive oil in a wide heavy skillet over medium-high heat. Add as many of the seasoned ribs as fit without touching. Brown them well on all sides, about 15 minutes total. Remove them to an 11 x 15-inch baking dish (or other dish in which they fit snugly in a single layer) and repeat with the remaining ribs.
Spoon the manchamanteles over the ribs, wiggling the dish so the sauce works its way between the ribs. Cover the dish with a sheet of parchment paper and then a sheet of foil, crimping the foil to the sides of the dish to make a tight seal. Bake until the ribs are fork tender, about 1 ¾ hours. Remove and cool to room temperature. Refrigerate 1 to 2 days. You could serve the ribs right away, but they will be noticeably better after a couple days when the flavor will have permeated every inch of the ribs. Also, the fat will rise to the top, making it easy to remove before reheating.
Bring the ribs to room temperature. Meanwhile, preheat the oven to 350 degrees F. Spoon/scrape the fat from the top of the sauce and ribs. Bake the ribs, uncovered, 20 minutes. Remove the baking dish from the oven and, very carefully, turn the ribs over in the sauce. Return to the oven until heated through, 20 to 25 minutes. (It's unlikely, but if the ribs appear even slightly dry, cover the dish after turning the ribs.) Spoon a little of the pan sauce over the ribs and serve them from the baking dish right away.