From the incredible Italian cookbook "Science in the Kitchen and the Art of Eating Well" by Pellegrino Artusi.
1 lb of eel
Kosher salt (for removing slime)
1 clove garlic
3-4 Coarsely chopped sage leaves
Peel of 1/4 lemon
Dry Red or White wine
Take an eel weighing about 1 pound or several adding up to the same weight; it is not necessary to use large eels for this dish. Rub them with kosher salt to clean them of mucus, then rinse and cut into log-like segments. Put a thinly sliced clove of garlic, three or four coarsely chopped sage leaves, the peel of a quarter of a lemon, and a little oil in a skillet. Put on the fire, and when the garlic has browned, put in the eel and season with salt and pepper. When the liquid starts to evaporate, keep moving the eel segments with the point of a knife so that they do not stick to the pan; once they are browned on one side, pour in some tomato sauce or diluted tomato paste and turn them. When they are browned on the other side, pour in a good finger of dry red or white wine mixed with two fingers of water, cover the pot and finish cooking the eel over a low flame. Send to table with a generous amount of their own sauce. This recipe serves four people.