Wash the oxtails well and place them in a large saucepan with water to cover. Place over high heat and bring to a boil. Reduce the heat and simmer until the oxtails are fork-tender, about 90 minutes.
Allow to cool. Then cover the pot and refrigerate overnight to separate the fat.
The next day, skim and reserve the fat for sauteing. Take the oxtails from the broth. Reserve the broth for later use.
Prepare the achuete water: soak seeds in a small bowl with hot water. After 30 minutes to an hour, pass the seeds through a sieve, reserving the orange-colored water for the saute.
In a large saucepan, over medium heat, warm 5 tablespoons of the oxtail fat or canola oil. Add the garlic, onions, and saute for about 5 minutes.
Add the tomatoes, achuete water and peanut butter and cook for 2 minutes or till tomatoes have softened.
Add the reserved broth and cook for 15 minutes to blend the flavors.
Add the oxtail and cook, uncovered for 20 minutes. Keep stirring the sauce so the ingredients do not stick to the bottom of the pan or get burned.
Once the oxtail has blended well, add the long beans and eggplants and cook for 10 minutes. Add the bok choy last because this will take 5 minutes to cook. The stew should have a thick sauce, not too soupy, but just the right amount of gravy-like consistency.
Serve Kare Kare over steamed white rice, accompanied with "bagoong"/shrimp paste on the side.