Heat the schmaltz in a large skillet over medium heat. Once it is hot, add the onions, season lightly with salt and pepper, and cook, stirring and scraping the bottom of the pan so the onion juices don't burn, until the onions are very soft and lightly caramelized, 20 to 30 minutes.

Crack the eggs into a medium bowl and whisk briefly to blend. Pour the eggs into the pan and immediately mix the eggs and onions together. Let the eggs cook for 1 to 2 minutes, until they start to set, and season lightly with salt and pepper. Once the eggs are set on the bottom, stir the mixture and continue cooking until the eggs are just cooked, keeping them in large curds, another 2 to 3 minutes.

Serve right away.