Wash and peel the beetroot. Cut into 3mm slices. Now cut each slice into batons. Slice the red onion finely. Place a medium saucepan on the hob and set to a medium-high heat. Add the cinnamon stick and cumin seeds, when the seeds start to sizzle add the curry powder, turmeric, ginger, green chilli, garlic and cayenne if using. Stir and cook for 30 seconds or so, then add the onion. Cook on a medium-low heat for 3-5 minutes.