Step 1 Peel the cipollini and place them on a baking sheet with a pinch of salt and a teaspoon olive oil. Roast in a 400-degree oven, turning occasionally for even browning, until brown and soft, about 45 minutes.
Step 2 Place the onions with the remaining ingredients into a blender or food processor (or into a deep bowl, if using an immersion blender). Blend until smooth. Taste and adjust the seasoning if necessary. Makes three-fourths cup.