Bring the sugar and water to a boil in a large pot.
Add orange slices, lower the heat and simmer for 2.5 hours.
Remove from heat.
Let cool in syrup overnight.
Make the Cake:
Preheat overn to 350 degrees.
Butter and flour a 10-inch springform pan.
Beat the eggs and sugar with an electric mixer for 10 minutes, until very thick and pale.
Gradually fold in the flour.
Fold 1/4 of the batter into the melted butter, then fold the butter mixture into the remaining batter.
Spoon the batter evenly into the prepared cake pan.
Bake in the center of the oven for about 35 minutes, until a cake tester inserted in the center of the cake comes out clean.
Cool on a wire rack.
Run a knife around teh edge of the pan to release the cake.
Remove the sides and the bottom of the pan.
Trim any crips edges and slice the cake horzontally into 3 thin layers.
Orange Bavarian Cream:
In a medium saucepan, heat the milk to simmering.
In a bowl, beat the yolks with 9 tablespoons of the sugar until well combined.
Gradually beat in the hot milk.
Stir in the softened gelatin.
Retrun the mixture to the saucepan and cook over low heat, stirring constantly with a wooden sppon for about 10 minutes, until the mixture thickens enough to coat the back of a spoon, (Do not let boil or the eggs will curdle.).
Stir in the vanilla and Cointreau.
Place the saucepan over a bowl of rice and stir until the mixture of mounds.
In a bowl, softly whip the cream with the remaining tbsp of sugar.
Carefully fold it into the chillled Bavarian mixture.
Line a 10" springform pan with plastic wrap, leaving a 5" overhang all around.
Drain the orange slices and reserve the syrup.
Choose the largest slices and place them in a decorative pattern on the bottom and sides of the pan.
Finely chop the remaining oranges and fold into the Bavarian Cream.
Spoon 1/3 of the Bavarian Cream over the oranges.
Place 1 layer of the cake over the cream and brush with some of the reserved syrup.
Repeat twice wtih the remaining cream and layers.
Cover with plastic wrap.
Place a 9" cake pan on top of the cake and put a 2 lb. weight in the center of the pan.
Refrigerate for at least 4 hours.
Remove the weighted pan and plastic wrap.
Invert the cake onto a serving platter.
Remove the sides and bottom of the pan and peel off the plastic wrap.