Toasted Hazelnut Romesco Dip

I can’t imagine a tapas bash without at least one dish accompanied by romesco, the famous pepper and nut sauce of the Catalan Tarragona province. In that region, one encounters dozens of variations on romesco, with ingredients that vary slightly, depending on how the sauce will be served. The version here—zesty with raw garlic, puckery with vinegar, and subtly spicy with dried chile—makes an ideal dip for crunchy green crudités, such as celery sticks, fennel sticks, or endive