Heat the oven to 180°C/Gas 4. Put the bulghur into a bowl of cold water and soak for about 30 minutes, changing the water once, then drain and squeeze dry. Peel and quarter the onion, then put it into a food processor and whiz until finely chopped. Add the bulghur, minced lamb, cinnamon and whisked egg. Season generously with sea salt and plenty of black pepper and whiz very thoroughly until you have a fine paste.
Turn the meat and bulghur mixture into a 25 cm earthenware dish and press down evenly with your fingertips. Scatter the pine nuts all over the surface and press them slightly into the mixture with the flat of your hand. Put the dish on a shelf towards the top of the oven and bake for 35-45 minutes until well browned on top. When ready to serve, cut into slices, like a flan.