Whisk together the pumpkin puree, sunflower oil, eggs and sugar in a large bowl until smooth. Sift together the flour, baking powder, baking soda, spices and salt. Tip the dry ingredients into the wet and fold together until smooth.
Place the egg white, water and vanilla extract in a bowl and whisk until it is frothy. Mix together the sugar, spices and salt in a separate bowl. Add the pecans to the egg white and stir thoroughly to coat then tip them into the sugar mixture and mix well.