Mix the garlic cut into strips, rosemary, pepper, wine and oil in a terrine. Put the meat in a deep dish, brush it with the prepared condiment and marinate for an hour. In a baking dish, season the rump cap with coarse salt and bake for 50 minutes in a preheated oven at 130° with the fat side up. Take out the baking dish, turn over the picanha with the fat side down and bake another 40 minutes. Strain the juices from cooking, add the red wine and reduce by half over low heat. Clean the celeriac, cut it and cook it in milk until soft. Drain and then blend it adding salt and extra virgin olive oil until you get a soft and smooth mousse. Put the celeriac mousse in the center of the plate, cut the picahna into cubes and serve drizzling the meat with its reduction sauce.