Sweet-and-sour pearl onions glazed with balsamic vinegar are a vegetarian Italian gem. This fresh mediterranean side is a healthy, elegant family accompaniment to roasted meats or fish.
Trim both ends of the cipolline or pearl onions. Blanch the onions in boiling water for 2 minutes, drain, and slip off skins.
In a large skillet over medium heat, add olive oil. Once shimmering, add onions in a single layer and sauté, stirring occasionally, for 5–7 minutes until just golden.
Sprinkle onions with kosher salt and black pepper. Stir well to evenly season.
Add sugar, balsamic vinegar, and water. Stir to combine, ensuring sugar dissolves. Increase heat to bring to a gentle simmer.
Reduce heat to low. Cover and cook for 15–20 minutes, turning onions occasionally, until they are very tender and the sauce thickens into a shiny glaze.
Uncover and let the onions cook for 2–3 more minutes, gently swirling the pan, until the glaze coats the onions evenly and any excess moisture evaporates. Serve warm or at room temperature.