Preheat the oven to 180ºC, fan 160ºC, gas 4. Line a 12-hole muffin tin with paper cases.
In a large mixing bowl, mix together the beetroot, sultanas, flour, sugar, baking powder and cinnamon, making sure the ingredients are evenly combined.
In a separate bowl, beat together the oil and eggs until combined, then pour into the dry ingredients. Mix together well, then spoon the mixture into the muffin cases, filling almost to the top.
Bake in the oven for 25 minutes, until just risen and a skewer inserted into the centre of one of the muffins comes out clean.