Ranch Potato Salad

3 lbs. red potatoes, peeled, cut into 3/4” chunks
3/4 c. mayonnaise
1/2 c. buttermilk
1/4 c. white wine vinegar
1/4 c. drained jarred roasted red peppers, finely chopped
3 Tbsp. finely chopped fresh cilantro
3 scallions, chopped fine
1 garlic clove, minced
1/8 tsp. dried dill
2 tsp. pepper
2 Tbsp. Dijon mustard

Bring potatoes, 1 Tbsp. salt and enough water to cover by 1” to boil in large pot over high heat. Reduce heat to medium and simmer until potatoes are just tender, about 10 minutes. While potatoes simmer whisk mayonnaise, buttermilk, 2 Tbsp. vinegar, red peppers, cilantro, scallions, garlic, dill, 1 tsp. salt, and pepper in large bowl. Drain potatoes, then spread in even layer on rimmed baking sheet. Whisk mustard and remaining vinegar in small bowl. Drizzle mustard mixture over hot potatoes and toss until evenly coated. Refrigerate until cooled, about 30 minutes. Transfer cooled potatoes to bowl with mayonnaise mixture and toss to combine. Cover and refrigerate until well chilled, about 30 minutes. Serves 6-8. (White or cider vinegar can be substituted.