Preheat the oven to 220°C/fan 200°C/gas mark 7. Put the cumin and coriander seeds in a pestle and mortar with the chilli and pound until ground. Add the cinnamon.
Put the crab meat in a large bowl with the spices, spring onions, parsley, dill, red pepper and lemon zest and mix well.
Lay out a sheet of filo and brush it with melted butter. Fold in half to make a rectangle. Put ¼ crab mixture in the top third of the rectangle and make a well in the centre. Crack in the egg, then fold the pastry over to encase the filling. Brush with butter and transfer to a baking tray. Repeat until you have 4 parcels.
Bake in the oven for 12-15 minutes, until golden brown and cooked. Dust with cinnamon. Stir the harissa through the yogurt and serve alongside the brik.