Preheat the oven at 175ºC/350ºF conventional oven and grease a 21,5 x 11,5 cm /8,5x4,5 inch loaf pan lined with parchment paper.
In a large bowl, stir together the all-purpose flour, granulated sugar, dark brown sugar, baking powder, baking soda, spices and salt. Give it a stir to make sure everything has been combined.
230 g all-purpose flour, 100 g granulated sugar, 150 g dark brown sugar, 1 teaspoon baking powder, ½ teaspoon baking soda, 1 ½ teaspoon ground cinnamon, ½ teaspoon ground ginger, ¼ teaspoon ground allspice, ¼ teaspoon ground nutmeg, ½ teaspoon salt
Add the baked sweet potato to a food processor and blend it until a smooth texture. Weigh out the puree and add it to a separate mixing bowl.
300 g baked sweet potato puree
Add the vegetable oil, eggs and vanilla extra to the sweet potato puree and with a hand whisk, whisk it together until combined.
110 g vegetable oil, 2 eggs, 1 teaspoon vanilla extract
Pour the wet ingredients into the dry while stirring it all together with a hand whisk or rubber spatula. Make sure there is no lumps left in the batter.
Pour the cake batter into the prepared loaf pan. Take a butter knife and insert it into the top of the batter in the loaf pan and run it a straight line down the middle.
Bake it for 1 hour and 5-15 minutes or until a cake tester comes out clean. Let the cake cool on a wire rack. After 10 minutes, gently remove the cake from the loaf pan and let it cool down completely.