Line 7½-8 inch (19-20cm) springform with parchment paper and grease the sides with oil or butter. Set aside.
In a bowl, combine sifted flour, salt, and baking soda. Set aside.
Using a mixer with the whisk attachment, combine eggs and sugar and mix until foamy. Add ricotta cheese, melted butter, vanilla, and the juice and zest of one orange (and orange oil if using). Mix again until incorporated.
To the wet ingredients, add the flour mixture, a little at a time. Mix until just incorporated, but don't overmix.
Transfer to the springform and bake for about 50 minutes (depending on your oven), or until a toothpick comes out clean.
Remove it from the oven and let it cool for a few minutes before removing the springform. After the springform is removed, transfer it to a wire rack to cool completely. You can also leave it overnight in a sealed container and add the frosting the next day.
Orange Syrup
While the cake is baking, make the syrup. In a saucepan, add the sugar and the juice of the orange (zest is optional). Cook on low for about 15 minutes, stirring frequently so it doesn't stick to the bottom. Let it cool while making the frosting.
Cream:
In a mixer with the whisk attachment, mix the mascarpone and cream cheese for a few seconds, add the heavy cream and powdered sugar, plus the juice from half the orange (zest is optional).
Assembling:
Using a bread knife or a cake cutter, cut the top rise of the cake so you have a flat layer. Then cut the cake in half to create two layers.
Using a pastry brush, spread the orange syrup on top of the bottom layer so it's nicely soaked, add half of the frosting, and cover with the top part. Again, add the orange syrup to the top layer, and spread the rest of the frosting to the top of the cake. Decorate with orange slices if desired. Enjoy!
Notes
You can store the cake covered in the fridge. Just let it come to room temperature before serving.
You can make the cake the night before, let it cool. Wrapped well in plastic wrap, transfer to a sealed container so it doesn't dry out, and leave at room temperature. Make the frosting the next day and finish the cake.
The orange syrup can also be made a day or two in advance. Let it cool completely before storing it in a sealed container. Keep it at room temperature or in the fridge.