- 2 T grapeseed or other neutral oil
- 6 onions, peeled and sliced (about 8 very loosely packed cups)
- large pinch kosher salt
- Heat the oil in a 12-inch cast-iron skillet over medium high heat for a minute to a minute and a half, until it’s very, very hot, but not smoking. Add the onions to the pan—they will be piled up high, probably to the rim of the skillet—and let them cook undisturbed for 2–3 minutes.
- Carefully toss the onions and, while doing so, season them with the salt.
Now you’ve got 50 or so minutes of onion cookery ahead of you, and given all the eccentricities of pans and heat sources and the variables of moisture in the onions, etc., the best I can do is tell you what you’re doing and what you’re looking for:
a. For the first 15 minutes or so, you want the onions at the bottom of the pan to be slowly but steadily taking on color as they sweat out liquid. The onions above them in the pan are helping this happen by virtue of their weight gently pressing down the onions beneath them. Do not press down on the onions with a spatula or jack the heat to try and accelerate this process. Just turn the whole pile of onions over on itself every 3 or 4 minutes during the early going to help distribute the tasty, caramelizing juice the onions are oozing throughout the pile.
b. After the mass of onions in the pan has significantly reduced in volume—the onions are softer and suppler and have fallen considerably—then it’s time to turn the heat to medium-low and ride this baby out for as long as it takes, stirring and turning the onions every 10 minutes or so and making sure that they don’t start to stick or burn at any point. This is the part that matters, when the onions soften and sweeten without drying out. Remember: slow and steady wins this race.
c. After 50 or so minutes, you’re going to be about there. The onions will have shrunk from a pile that threatened mutiny to the stovetop to a huddled mass that doesn’t even cover the floor of the pan. They will have a definite sweetness, a deep, roasted flavor, and a texture that’s just this side of mushy. Use them straight away or let them cool and then store, tightly covered, in the refrigerator.