Make these quite a bit. I get the rack of ribs from Waitrose, I am not keen on fat and any thats there tends to cook away.
I make a rub, no idea on exact quantities but as a guess for 2 racks, bash a teaspoon of fennel seed and add salt & pepper, 3 teaspoons of paprika, teaspoon of oregano and rub in. I put in a roasting tray and grate over an apple or two depending on size. Then add some orange or apply juice to the tray and the same of water (about a glass of each, depending on size of tray).
Cover with foil and cook for around 3 at about 120/130c. Then I put some Reds Kansas City BBQ sauce over and brush on. put back in for another 30 mins, and then add more sauce, take the foil off and maybe do once more, or at least add more sauce at the end (scrape of most of the apple).
They just fall apart.