Preheat the oven to 160C/325F/gas mark 3
Use an 18cm/7 inch round cake tin.
Lightly grease and line the tin. Peel the pumpkin, chop roughly and cook in 150ml/ 1/4 pint boiling water for 2-3 minutes until tender. Drain well and mash. Beat the margarine, sugar and golden syrup together in a mixing bowl until light and fluffy. Gradually add the soya milk. Stir in the pumpkin and nuts. Sift the flour and cinnamon together over the mixture and carefully fold in using a spatula. Place the mixture in the prepared tin, smooth the top and bake for 70 to 75 minutes, or until cake springs back when pressed in the centre. Cool in the tin for ten minutes. Turn out onto a wire rack.
Topping: Heat the syrup and cinnamon in a small pan. Bring to the boil, then remove from the heat. Brush the top of cake with the glaze and decorate with pecan nuts and pumpkin seeds. Brush the nuts and seeds with more glaze.