Preparation / Directions:
Preheat oven to 350.
Rinse the orange, slice thin, and place in a pot. Pour in just enough water to cover the slices, bring to a boil, put a lid on top, and simmer about 15 minutes, or until the rinds are completely soft. Place a strainer over a bowl and pour the cooked oranges and their water into the strainer. Leave to drip thoroughly. Reserve the orange water.
Select an 8- or 9-inch-square cake pan and sprinkle in the brown sugar. Add the butter and 2 tablespoons of the orange water. Place the pan in the oven to melt the butter and sugar. Stir with a fork to spread the syrup evenly in the pan. Put aside.
Prepare the batter: Cream together the butter and granulated sugar. Add the egg, vanilla, cinnamon, and 2 tablespoons of orange water and beat well. Resift the flour with the baking powder and salt and add to the creamed ingredients alternately with the milk. Begin and end with the dry ingredients.
Arrange the cooked orange slices in rows in the syrup at the bottom of the cake pan. Place the slices side by side or overlapping, but do not allow them to touch the sides of the pan. Spoon the batter over the oranges carefully so as not to disturb the pattern. Smooth the batter into an even layer with a rubber spatula. Bake about 30 minutes, or until a toothpick plunged in the center comes out clean. Remove the cake and allow it to cool for 10 minutes. Reverse the cake onto the serving platter and allow to cool completely.