In a large bowl, combine the mayo and sour cream until well blended. Then mix in the chopped beef, parsley, dill, onion flakes, garlic powder, and salt.
Cut out a large circle in the top of the rye bread, and remove the interior of the rye loaf to form a bowl.
Place the dip mixture in the bread bowl.
Cut the extra bread into strips then toast to firm them up.
Serve immediately with toasted bread for dipping.
Notes
The removed bread chunks can be easily toasted in the oven, under a broiler, or in a toaster oven.