Bring a large pot of water to the boil. Add a large pinch of salt and cook the pasta as per the packet directions until al dente.
Drain the pasta and rinse it under cold water. Drain well again, then place into a large bowl.
Add the flaked tuna, chopped celery, red onion, cucumber, cherry tomatoes and peas.
Make the dressing by mixing the whole egg mayonnaise, sour cream, dill, lemon juice and salt and pepper in a bowl.
Pour half of the dressing over the pasta salad and stir to combine (see notes).
Just before serving, mix the remaining dressing through the tuna pasta salad.