Preheat the oven to 180°C/160°C fan/350°F/gas mark 4. Place a 10-12 cup bundt tin in the fridge for 15 minutes then thoroughly brush it with melted vegan butter making sure that you get right into all of the nooks and crannies.
Whisk together the plain flour, light brown soft sugar, caster sugar, baking powder, bicarbonate of soda, pumpkin spice and salt in a large mixing bowl. If the brown sugar is lumpy make sure that you break up the lumps.
Add the pumpkin puree, oil, non-dairy milk, vinegar and vanilla extract and whisk gently until no dry lumps remain but be careful not to over-mix.
Transfer the batter to the prepared tin and spread it level. Bake for about 50 minutes until a skewer inserted into the centre comes out clean or with a few moist crumbs but no wet batter.
Leave the cake to cool in it's tin on a wire rack for 45 minutes before carefully flipping it out onto a wire rack and leaving it to cool completely.
To make the maple glaze, sift the icing sugar into a bowl and add the maple syrup. Gradually stir in enough milk to form a thick but pourable glaze. If it is too thin it will run right off the cake so be careful not to add too much.
Place the cake on a serving platter and drizzle over the glaze. Top with chopped pecans if you like.