Preheat the oven to 100C/210F/Gas ¼. Grease and line a 900g/2lb loaf tin.
Place the pumpkin in a roasting tray and drizzle with the olive oil. Cover with foil and roast for 25 minutes. Remove from the roasting tray and set aside to cool. Blend the pumpkin in a food processor until smooth.
Increase the oven to 180C/350F/Gas mark 4.
Cream the butter and sugar until light and fluffy. Add the eggs and pumpkin and stir until well combined.
Stir in all the dry ingredients and place the mixture into the loaf tin. Bake for 50 minutes. Remove the tin from the oven. Once cool remove the loaf from the tin.
Sprinkle with icing sugar and cinnamon, slice and serve with Greek-style yoghurt.