Preheat the oven to 180°C fan (350°F). Grease a 2lb loaf tin with some oil and line with a sling of baking paper.
In a large bowl, mix the pumpkin puree, sugar, oil, spices, orange zest and salt until smooth.
200 g (3/4 cup plus 1 tbsp) pumpkin puree*, 150 g (3/4 cup) light brown sugar*, 90 g (1/3 cup + 2 tsp) neutral oil or light olive oil, 2 tsp ground cinnamon, 1/2 tsp freshly grated nutmeg, 1/2 tsp ground ginger, 1/8 tsp ground cloves, zest of 1 orange, 1/4 tsp fine table salt
Stir in the sourdough starter. Lastly, add the flour and bicarbonate of soda. Fold together until just combined.
150 g (3/4 cup) sourdough starter/discard, 120 g (1 cup) plain white (all-purpose) flour, 1 tsp bicarbonate of soda
Pour the batter into your lined loaf tin. Sprinkle with the topping of light brown sugar and pumpkin seeds, if using.
2 tbsp light brown sugar, 3 tbsp pumpkin seeds/pepitas
Bake for 55-70 minutes- a toothpick inserted into the centre should come out clean. If the loaf looks like it's browning too much but is not cooked through yet, tent the top with foil for the last 20 minutes of baking.
Allow to cool before removing from the tin, slicing & serving.