Whisk together all the ingredients until smooth and well combined. Pour the batter into the prepared loaf pan.
1 ¾ cups (210 g) all-purpose flour, 1 cup (227 g) pumpkin puree, ¾ cup (149 g) granulated sugar, ¾ cup (160 g) light brown sugar, ¾ cup (175 g) sourdough starter, ½ cup (99 g) coconut oil, ⅓ cup (76 g) water, 2 (100 g) large eggs, 1 teaspoon baking soda, 1 teaspoon ground cinnamon, 1 teaspoon pure vanilla extract, ½ teaspoon ground nutmeg, ½ teaspoon salt