Peel and slice the onion. Separate the slices into rings.
Pat the livers dry with paper towels, cut them in half, then trim and discard any visible fat or green parts. Wash your hands well after handling the raw livers.
Heat the olive oil over medium heat until it shimmers, about 2 minutes. Add the onions and sprinkle them with half the kosher salt. Saute the onions, stirring often, until golden brown, about 10 minutes.
Remove the onions to a plate and cover them to keep them warm, or place them in the oven on the "keep warm" setting.
Add the cleaned livers to the same skillet. Sprinkle them with the remaining kosher salt and ¼ teaspoon of black pepper.
Cook the livers over medium heat until browned but slightly pink in the middle, about 3 minutes per side. (See notes).
Divide the cooked livers between plates, top them with the onions, and serve.
Video
Notes
If added to a too-hot pan, the livers will splatter and even burst. So make sure to use medium heat and don't wait too long before adding them to the pan.
There's no need to rinse the livers, soak them, or coat them in flour.
The USDA recommends cooking poultry internal organs to an internal temperature of 165°F.
You can add more spices if you wish, such as ½ teaspoon of garlic powder, ½ teaspoon of paprika, and ¼ teaspoon of cumin.
You can keep the leftovers in an airtight container in the fridge. Since they are still pink in the middle after I cook them, I don't like to keep them for longer than a day. I either reheat them covered in the microwave or mash them cold with softened butter to make a pâté.
I don't recommend freezing the leftovers. Their flavor and texture will be off after freezing and thawing.