Loin of Pork in Balsamic Vinegar Recipe

Sauté the onion in 1 tablespoon of the olive oil, add the vinegar and a pinch of sugar. Cook until the onion is completely soft and purée. Set aside.
Heat the sage in the remaining 2 tablespoons of oil. Brown the loin on all sides and cook for 5 or 6 minutes. Remove the fillet and slice into 3/4-inch slices. Put back into the pan, pour the balsamic dressing over the meat, and cook until the pork is done, another 5 minutes.