Bring a large pot of salted water to a boil over medium-high heat. Add the elbow macaroni and cook until al dente, about 7-8 minutes. Drain and rinse briefly under cool water. Set aside to cool.

In a mixing bowl, combine the mayonnaise and yellow mustard. Whisk until smooth and creamy.

Fold in the chopped celery and diced onion, then gently mix in the cooled macaroni until evenly coated.

Season with salt and pepper to taste, mixing well.

If the salad is thick, gradually add reserved pasta water, mixing until the desired consistency is reached.

Cover the bowl and chill in the refrigerator for at least 1 hour before serving.

Give the salad a gentle stir before serving. Transfer to a serving bowl and enjoy with your favorite summer dishes.