- Preheat your oven to 350°F (175°C). Grease and flour a 9x5-inch loaf pan. 
- In a large mixing bowl, combine the mashed sweet potatoes, granulated sugar, brown sugar, vegetable oil, eggs, and vanilla extract. Mix until well combined. 
- In a separate bowl, whisk together the flour, baking powder, baking soda, cinnamon, nutmeg, and salt. 
- Gradually add the dry ingredients to the sweet potato mixture, stirring until just combined. Be careful not to overmix. 
- If using, fold in the chopped nuts and raisins or dried cranberries. 
- Pour the batter into the prepared loaf pan and smooth the top with a spatula. 
- Bake for 60-70 minutes, or until a toothpick inserted into the center comes out clean. If the top starts to brown too quickly, cover it loosely with aluminum foil. 
- Allow the bread to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.