Boil the oranges in a covered pot for 2 hours; ensure water covers them as much as possible – check a few times, as you may have to add water if it evaporates. Preheat oven to 350F. In a blender or food processor, blend all wet ingredients until smoothly pureed. In a large mixing bowl, combine dry ingredients and stir to mix evenly, then add wet ingredient and fold to combine until completely incorporated. Grease a tall cake dish or bundt pan (mine was 8″ diameter and about 3″ deep), then sprinkle brown sugar and sliced almonds evenly in the bottom. Pour in the cake batter and bake for 45-55 minutes, until browned on top and springy to touch.