* ½ pound onion, finely chopped (2 cups)
* ¾ tsp salt
* ¼ cup olive oil
1. In a strainer, toss the onions with the salt. Cover them with a paper towel and weight down with a bowl or plate topped with a heavy object, like a large can of tomatoes. Let the onions drain for at least 30 minutes, tossing them occasionally. Place the onions in fresh paper toweling or a clean kitchen towel and squeeze out as much liquid as possible.
2. Warm the oil in a heavy 8-or 9-inch skillet. Add the onions and cook, uncovered, over the very lowest heat. As their moisture evaporates, the onions will shrink considerable and the ever-deepening gold oil will appear to increase. Stir occasionally, spreading the onions out in the skillet and making sure that they do not stick or color past gold. After cooking for 60 to 75 minutes, they should be very soft and have exuded most of their liquid. Let the mixture cool slightly, then scrape all the onions and oil into a blender (a food processor won't work well here).
3. Blend to emulsify the ingredients, stopping to scrape down the contents of the blender when necessary. Continue blending until you have a smooth, rich puree.
4. Store tightly covered in the refrigerator. It will thicken and become more "schmaltz"-like when chilled. It will keep for as least 3 to 5 days.