Classic Macaroni Salad - Six Sisters' Stuff

Ingredients

• 2 cups dry elbow macaroni (cooked, rinsed and drained)
• ⅓ cup diced celery
• ¼ cup minced red onion (soaked in cold water for 5 minutes, drained)
• ¾ cup shredded carrots
• 1 Tablespoon minced flat-leaf parsley
• ½ cup diced vine ripened tomato (optional)
• ½ cup prepared mayonnaise
• ¾ teaspoon dried mustard
• 1 ½ teaspoon sugar
• 1 ½ Tablespoons cider vinegar
• 3 Tablespoons sour cream
• ½ teaspoon kosher salt (plus more to taste)
• Freshly ground black pepper