To make the batter for the orange tart, first mix the yolks with the egg whites, sugar and a pinch of salt in a small baking bowl. Place the baking bowl in a water bath at low temperature and mix the egg mixture with a mixer until it is lukewarm.
Remove from the water bath and continue beating until the mixture is fluffy and creamy. This will take about 40 min in total. Melt the butter and let it cool. Using a wooden spoon, fold the flour sifted with the maizena (cornstarch), the butter and the orange zest into the egg mixture.
Grease and flour a flower mold (O 23 cm) with butter. Line the bottom with parchment paper. Pour the dough into the mold and bake at 180 °C for 45 min.
For the filling, rinse the oranges and cut into slices with peel. Put them in a saucepan, cover with water and cook until there is no liquid left in the pan. Add the jelling sugar and simmer for half an hour at low temperature. Let the jam cool, cut the cooled dough into three parts. Spread two parts with the orange marmalade and assemble the cake.
Dust with powdered sugar and serve the orange tart.