Preheat the oven to 200°C.
Remove meat from the lamb neck, chop the bones, and roast them in a tray until browned.
Sauté carrot, onion, and garlic in a stockpot with olive oil until browned.
Stir in herbs, salt, and tomato purée, cooking for two minutes.
Add roasted bones and 2 liters of water, simmer for one hour, and skim fat regularly.
Strain the liquid and reduce it to 1 liter of stock.
Lower the oven temperature to 150°C.
Slice lamb into 2cm thick pieces, dust with flour, and fry in oil until colored.
Fry the remaining onion, carrots, and garlic in the same pan.
Layer lamb, vegetables, herbs, and seasoning in a casserole dish, adding stock between layers.
Top with sliced potatoes and knobs of butter.
Cover and bake for 90 minutes, then uncover and bake for 45 minutes more.
Mix red cabbage ingredients in a tray, cover with foil, and bake for 90 minutes.
Serve the hotpot with the braised red cabbage on warm plates.