Place the oranges in a medium sauce pan and cover with water. Bring the pot to a boil then cover, reduce heat to low, and simmer until oranges are soft, about 2 hours.

Once the oranges are cool enough to handle, slice them in half and remove any large seeds.

Preheat the oven to 350 degrees.

Place the oranges in a blender and pulse until smooth. You should end up with about 1 1/2 cups of puree. Add the remaining ingredients, except for the powdered sugar, to the blender. Pulse a few times, stir, and then pulse, repeating until the mixture is well combined.

Grease an 8 inch round spring form pan. Pour the cake batter into the pan and bake for 45 minutes to an hour, or until a toothpick inserted in the center comes out clean.

Allow the cake to cool, then sprinkle with powdered sugar, if desired. Or frost with your favorite frosting.