Preheat the oven to 350 degrees Fahrenheit. Grease a 9x13 pan with non-stick baking spray.
Boil 3-4 medium sweet potatoes until fork tender. Allow to cool then peel and mash.
In a medium size bowl, mix the flour, baking powder, salt, cinnamon, salt and nutmeg. Stir and set aside.
In a large bowl, mix the sweet potato, sugar, brown sugar, eggs, vanilla extract, buttermilk, and oil. Whisk until well combined.
Add the dry ingredients into wet ingredients then mix until fully combined.
Pour the batter into the greased pan. Bake for 25-30 minutes or until a toothpick comes out clean.
While the cake is baking, let’s make the frosting. In the bowl of a stand mixer, beat cream cheese, powdered sugar, vanilla, and salt until combined, about 2 minutes. Lastly add in the chopped pecans. Place the frosting in the refrigerator until the cake is completely cooled.
Once the cake is cooled, top the cake with a generous amount of frosting.