Cook pasta according to package instructions. During the final 3 minutes of cooking, add the frozen peas. Drain, rinse with cold water and put in a large serving bowl.

Mix together cottage cheese, mayonnaise, and buttermilk in a blender until soft. Add the dill and salt, then keep aside.

Add to the paste and pea bowl tuna flakes and celery. Pour over the cottage cheese mixture then mix well.

Cover and chill for 1hour before serving.