Preheat oven to 180 degrees C. Coat a 10 cup fluted ring tin with cooking spray.
Stir flour, baking powder, bicarbonate of soda, salt and cinnamon in a small bowl.
Beat sugar, oil, eggs and pumpkin in a large bowl until well combined. Beat in flour mixture until evenly moistened. Beat in whiskey. Using a rubber spatula scrape the batter into the tin.
Bake until a skewer inserted in the cake comes out clean; about 45 to 50 minutes. Transfer tin to a wire rack then leave the cake to cool in the tin for 15 minutes. Run a thin-bladed knife around the edge and centre ring of the tin. Turn out cake onto rack and leave to cool completely. Dust with icing sugar.