You can bake this in a square or loaf pan. Double the recipe for a 9x13 inch / 23x33 cm cake. Refrigerate any leftover pumpkin puree in the fridge for up to three days or freeze for later use. You can vary this recipe by adding up to 1 cup / 250 ml of add-ins: chopped cranberries, nuts, pumpkin seeds, candied ginger... You can also change the spices and top with a glaze or frosting instead of the cinnamon sugar.
Preheat oven to 350 degrees F / 177 degrees C. Lightly grease an 8x8 inch / 20x20 cm or 9x5 inch / 23x13 cm pan.
In medium mixing bowl, stir together all-purpose flour, chickpea flour (or additional all-purpose flour), white and brown sugars, cinnamon, baking powder, baking soda and salt.
In separate bowl, beat pumpkin puree, oil, water, vanilla and vinegar.
In small bowl, stir together the one tablespoon of sugar and 1 teaspoon of cinnamon. Set aside.
Add the pumpkin mixture to the dry ingredients and stir gently until thoroughly mixed. The batter will be stiff so make sure to bring the dry ingredients up from the bottom of the bowl so that they will be mixed in. Do not overmix the batter.
Spread the cake batter in the prepared pan and sprinkle with the cinnamon sugar.
Bake for 40 to 45 minutes or until an toothpick inserted into the center of the cake comes out clean. Cool cake in pan and serve.