Cut the neck of the pork lengthways in such a way that a roulade is approx. 2 - 3 cm thick. Season with spit roast spices on both sides.
Cut the onions into rings and season with salt (a little), paprika and cayenne pepper. Mix well until they are evenly slightly reddish. Then cover the pork neck with about 1/4 to 1/3 of the onions. Incisions or pockets that have been made when slicing are good to accommodate a slightly thicker amount.
Roll up the neck of the pork and tie it to a roll roast with kitchen twine.
If necessary, season again on the outside, pack in a large bag and let it steep in the refrigerator for at least half a day. I always finish the roast a day earlier and let it sit until the next day. Put the remaining onions in the refrigerator in a bag or a sealed can.
Take the roast out of the bag and fry in oil or clarified butter on all sides until it has a nice color. Briefly remove the roast and let the remaining onions in the pan briefly take on color. Add the roast again and pour in the broth. With the lid closed, simmer for 2 - 2.5 hours, depending on the thickness. Turn it every 30 minutes.
Towards the end of the braising time, peel the potatoes, cut them into slices and then fry them in a little clarified butter until they are done (20-30 minutes). Season with salt, pepper and paprika towards the end.
If necessary, season the onion sauce with a little salt, pepper and paprika and thicken to the desired consistency. Slice the roast and serve with the fried potatoes and onion sauce.