Step 1

In a nonreactive 12-inch skillet, combine the oil, onions, sugar, vinegar and 1 teaspoon salt. Cook over medium-high, uncovered and stirring occasionally, until the pan is almost dry and the onions are slightly softened (they will retain some texture, not turn jammy and soft), about 15 minutes.

Step 2

Transfer to a bowl or container and let cool. In an airtight container in the refrigerator, the onions will keep for up to 1 week; bring to room temperature before serving.