Boil Water: Boil water with a teaspoon of salt per quart for the pierogi.
Sauté Onions: Peel and slice onions, then sauté in butter or oil until translucent (6-10 minutes).
Cook Pierogi: Boil the pierogi according to the recipe or package instructions. Or do the following: wait until they float to the surface, then continue cooking for 2-4 more minutes.
Dry Pierogi: Drain and dry the cooked pierogi on a plate for 1-2 minutes on each side.
Combine and Cook: Add pierogi to the onions in the pan and cook on medium heat for 3-5 minutes, flipping once for even browning.