Cook the elbow macaroni pasta according to the package instructions. Once cooked, drain the pasta and rinse with cool water to stop the cooking process. Set aside.
Run the frozen peas under hot water to thaw them quickly. Drain any excess water and set aside.
In a large mixing bowl, combine the cooked macaroni pasta, mayo, mustard, shredded cheddar cheese, onion powder, thawed peas, and chopped hard-boiled eggs. Mix until everything is well combined and the sauce is smooth and creamy.
Once mixed, taste the salad and adjust seasoning if needed.
Serve immediately, or refrigerate for a few hours to allow the flavors to meld together.