Place rabbit in a glass bowl or baking dish. Cover with water, vinegar and onions, and season with salt, pepper, tarragon and cloves. Let stand for 24 hours or at least overnight.
Melt butter in a heavy saucepan over medium-high heat. Add rabbit pieces and brown them on all sides. Reduce heat to medium and pour in enough of the marinade to cover the bottom of the pan. Add more marinade as needed. Cover pan and simmer for 20 to 25 minutes, or until meat is tender and the juices run clear.
Remove meat to a deep platter, and stir the sour cream into the juices in the pan. Cook over high heat, stirring constantly until gravy is thick and smooth. Pour over meat and serve immediately.