Prepare the oven at a high temperature.

Prepare a dish for the meat and place it to cook in the oven.
Prepare the meat for the oven, put the pepper, salt, and oil over the meat.
Peel the onion and quarter and place in the dish with the meat.
Place in the oven about 20 minutes.
Prepare in the mortar the garlic and parsley and crush together.

When the meat has ben cooking some 20 minutes remove the dish from the oven. Be careful to put on cooking mittins) Put on top of the meat the garlic and parsley half of the wine and water., y un poco de sal.

Lower the oven temperature to 225º and return the meat for another 10 minutes.
After the ten minutes remove the meat and add the rests of the wine and water and taste to see if it is to taste.

Now all you need do is wait 10 to 15 minutes while the sauce reduces.
After the meat is roasted remove it and allow it to cool.

When you have the meat cooled place it on a cutting board and prepare a well sharpened knife.
Slice the meat in fine pieces.

Place the lices in a clay dish if posible and put the sauce on top.
Sif the meat is a little rare for your taste you can put it on the burner and cook a bit longer.

The onion you can remove if you prefer, you can use potatoes(fried or baked) as garnish surrounding the meat.

If you choose the baked potatoes take advantage of the oven while you cook the meat and cook the potatoes at the same time.