Special equipment: bundt pan
Preheat oven to 325 degrees F.
a 10-cup bundt pan
In a mixing bowl, whisk together the flour, baking powder, cinnamon, and salt. Set the mixture aside. In a separate large mixing bowl, mash
the sweet potato, leaving only a slight meaty texture. Whisk
together the sweet potato and the eggs
. Whisk in the warm water, then the sugar, then the oil followed by the vanilla extract. Stir in the dry ingredients until homogenous then fold in raisins and walnuts. Spoon the batter
into the prepared bundt pan. Bake until a toothpick inserted into the center of the cake comes out clean, about 1 hour. Let the cake cool in the tin for 15 minutes and invert onto a serving platter or cake stand.