We make quick skillet meals like this one of sausages with onions and apples (and sometimes pears) when we are short on time and have either our own fresh sausages on hand or good ones that we buy. Small butcher shops sell wonderful fresh sausages, of course, but when we buy sausages at the grocery store, we get fresh ones from the butcher department rather than the ones that come in the Cryovac packages in the meat case. If the market is good, it usually has a nice selection of fresh sausages.
Adapted from "Canal House Cooking Volume No.5" by Melissa Hamilton and Christopher Hirsheimer.
Heat the oil in a large heavy skillet over medium heat. Add the onions cut side down, cover, and cook until just tender and browned on the bottom, about 15 minutes.
Tuck the sausages and apples around the onions in the skillet. Season with salt and pepper. Use two skillets if everything is too crowded together. Cook over medium heat, turning the sausages and apples as they begin to brown, but leaving the onions in place. Take care to leave the onion halves whole. Continue cooking until everything is nicely browned, then reduce the heat to medium-low.
Cover the skillet and cook until the sausages are cooked through and the apples and onions are tender, 5–10 minutes. Adjust seasonings. Serve garnished with fresh sage, if you like.