In a bowl, mix together the ground cinnamon and flour. Add the lamb pieces and toss in the mixture until coated all over.
Heat the oil in a large, heavy-based pan or casserole, add the spiced lamb and chopped red onion and cook for 5 minutes until nicely browned all over.
In a separate jug, make up 500 ml chicken stock using the stock cube. Add the tomato purée, chicken stock, apricots, chickpeas and peppers. Stir to combine. Bring to the boil, then reduce the heat and simmer for 30-40 minutes, until the lamb is tender and the sauce has thickened.
Cook's tip: to freeze, allow the tagine to cool completely, then transfer to a freezer container and freeze for up to 3 months. Thaw completely and reheat gently in a pan with a splash of stock, until piping hot.