Sear meat well in hot fat in a Dutch oven or heavy skillet on top of the stove. Transfer to a roasting pan. Peel carrots and cut in 1-inch round slices. Place them around the meat. Add prunes, apricots and lemon slices. Peel sweet potatos and cut in 1-inch slices. Place over meat and fruit in the roaster.
Add orange juice to boiling water. Combine brown sugar and flour and add enough water to make a thin paste. Add this paste to the orange juice mixture. Pour over the Tzimmes. If necessary, add more boiling water to bring liquid to the top of the tzimmes.
Cover. Bake at 400 degrees for 1 hour. Reduce heat to 325 F. and continue baking 4 1/2 hours. Uncover and bake 30 minutes longer.