
Cook macaroni per package instructions. Drain and rinse well. Let cool while working on the sauce. After cooling, refrigerate until ready to use.
In a small bowl, whisk mayonnaise, lemon juice or vinegar, sweet pickle relish, and mustard. Set aside or refrigerate until ready to use.
When ready to assemble, remove the macaroni from the fridge.
Mix the macaroni, tuna, celery, eggs, red bell pepper, peas, and onion in a large bowl.
Add the prepared mayonnaise sauce to the bowl and mix thoroughly.
Adjust salt and pepper to taste. And then add parsley for garnishing.
Serve or store in a tightly sealed container for 4-5 days. If the salad seems dry, add a couple of tablespoons of mayonnaise to moisten.