Traditional American Macaroni Salad

INGREDIENTS

2 cups

dry elbow macaroni, cooked, rinsed, and drained

1/3 cup

diced celery

1/4 cup

minced red onion, soaked in cold water for 5 minutes, drained

1 tbsp

minced flat-leaf parsley

1/2 cup

diced vine-ripened tomato (optional)

1/2 cup

prepared mayonnaise

3/4 tsp

dry mustard

1 1/2 tsp

sugar

1 1/2 tbsp

cider vinegar

3 tbsp

sour cream

1/2 tsp

kosher salt, plus more to taste

Freshly ground black pepper