Preheat the oven to 350degrees F.
Lightly butter and flour two 9-by-5-inch loaf pans.
Mix the dry ingredients in a large bowl.
2 ½ cups all-purpose flour, 1 ½ cups sugar, 2 teaspoon baking powder, 1 teaspoon baking soda, 2 teaspoon salt, 1 teaspoon cinnamon, 1 teaspoon nutmeg
In another bowl, whisk together the eggs, cooled melted butter, applesauce, sour cream, vanilla extract, citrus zest.
4 eggs, 8 oz butter, ½ cup applesauce, 1 cup sour cream, 1 teaspoon vanilla extract, 1 teaspoon citrus zest
Stir the sweet potato puree into the egg mixture, then fold into the dry mixture (and nuts if using) until just combined.
2 cups sweet potato puree
Stir in nuts, if desired.
1 cup chopped walnuts or pecans
Spread the batter into the prepared pans.
Bake until a toothpick comes out lean, about 55 minutes.
Wait 5 minutes, then turn out onto a wire rack to cool.