Heat a skillet over a medium heat and cook the onions with ½ teaspoon of the rosemary, stirring occasionally, until soft and golden brown, about 10 minutes. Season to taste with sea salt and freshly ground black pepper while it cooks.
2 onions, ¾ teaspoon fresh rosemary leaves, Sea salt and freshly ground black pepper to taste
Set the cooked onions aside, season the livers to taste with salt and pepper and cook them in the skillet with a bit more cooking fat until just browned, about 2 minutes per side.
1 lb chicken livers, Cooking fat
Set the livers aside and add the grapes with the remaining rosemary and cook for about 1 minute.
1 ½ cups seedless grapes
Now deglaze the skillet with the apple cider vinegar and stir to get all the browned bits.
⅓ cup apple cider vinegar
Melt in one last tablespoon of cooking fat and season to taste with sea salt and freshly ground black pepper.
Cooking fat, Sea salt and freshly ground black pepper to taste
Serve the livers and onions covered with the grapes and the sauce.