Line a roasting pan with foil. Rinse the oxtails with water and place them in the roaster.
Sprinkle lightly with cayenne (I usually use paprika), black pepper and salt.
Bake, uncovered, at 450 degrees for one hour, turning them over occasionally so that they become nicely browned.
Remove from oven and drain off all the fat. Set aside.
Combine the onion, garlic and oil in a blender (or food processor). Process until the onion is finely chopped. Place this mixture in a 2 gallon vessel and cook over medium heat until it becomes translucent.
Add the flour and wisk for about 30 seconds.
Add 5 1/2 cups water. Whisk until the flour dissolves.
Add tomatoes, Kitchen Bouquet and beef base.
Bring gravy to a slow boil.
Add the oxtails and carrots and simmer for 2 - 2 1/2 hours until the meat comes off the bones easily. Check for salt. Serve hot.
Note: The recipe lists tomatoes in the directions but not in the ingredients, so I just added 2 diced tomatoes when I have made this. I also add some celery, but that isn't in the original recipe.