- 5 tablespoons finely chopped red onion
- 1/4 cup white wine vinegar
- 1 teaspoon sugar
- Pinch of kosher salt plus more
- 1/4 cup buttermilk
- 1/4 cup sour cream
- 2 tablespoons chopped fresh chives
- 1/2 cup crumbled blue cheese
- Freshly ground black pepper
- Place onion in a small heatproof bowl. Bring vinegar, sugar, salt, and 1/4 cup water to a boil. Pour over onion; stir to coat. Cover; let pickle in the refrigerator for at least 1 hour.
- Whisk buttermilk, sour cream, and chives in a medium bowl until smooth. Stir in blue cheese. Drain pickled onion and stir into dip. Season with salt and pepper. DO AHEAD: Can be made 3 days ahead. Cover dip and refrigerate.