This dish was in my very first cookbook, a little tome published in 1982, now out of print. One day not long ago, someone called me on the radio and said she’d made it and loved it. I cooked it again and found out why.
Preheat the oven to 400 degrees F. If you have a convection oven, set it on convect. Cut off the root ends of each onion, about one-fourth the way down. Scoop out the centers of the onions, leaving ¼-inch-thick onion shells. Chop the onion centers.