Pre-heat your oven to 180°C/160°C fan.Line muffin tins with 12 cupcake cases. If you're using pumpkin/squash rather than purée then coarsly grate the pumpkin/squash (150g).
Beat together the oil (150ml) and brown sugar (135g) until combined.
Beat in the egg (2 large) until combined.
Sift in the self-raising flour (165g), bicarbonate of soda (½ tsp) and pumpkin spice (1½ tsp). Fold the dry ingredients into the egg, oil and sugar mixture until combined.
Add the grated pumpkin or pumpkin purée into the cake mixture. Fold together until combined.
Divide the mixture between the 12 cupcake cases. Bake for 20 minutes. Check the cupcakes are cooked through by inserting a skewer into the centre. If it comes out clean they are ready, if not, pop them back into the oven for a couple more minutes.
Move them to a cooling rack to cool completely.