Bring a large pot of salted water to a boil, add the medium shells pasta, and cook for 7-8 minutes until al dente. Drain and rinse under cold water.

Finely chop red onion, celery, and red bell pepper. Soak chopped onion in cold water for about 5 minutes if desired.

In a mixing bowl, combine cooled pasta, imitation crab meat, thawed peas, and chopped vegetables. Stir gently to combine.

In a small bowl, mix mayonnaise and fresh dill until smooth. Pour over pasta mixture and fold gently.

Season with salt and pepper to taste. Cover and chill in the refrigerator for at least 1 hour.

Serve chilled, garnished with chopped chives. Optionally drizzle with lemon juice.