Preheat oven to 190 degrees C. Grease and flour a ring tin. Sift together flour, soda, baking powder, cinnamon and salt. Set aside.
In a large bowl, combine oil and sugar. Add eggs one at a time and mix well. Add the flour mixture and beat until smooth. Add nuts and pumpkin and blend until smooth. Pour batter into ring tin.
Bake for 1 hour or until a toothpick inserted into the centre of cake comes out clean. Cool in pan for 10 minutes, then turn out onto a wire rack and finish cooling. Dust with icing sugar before serving.
Turns out really well. It's quite a big cake and keeps very well (if you don't eat it all at once)! I had to substitute some SRF for plain as I didn't have any baking powder and added a tiny bit more carb soda, hoping this would make up for the lack. Also without walnuts but still delicious. - 17 Jun 2014