This is a refined version (2) of the “greasy” Schiacciata recipe of olden days, which is prepared in Florence at Carnival time. In the old recipe suet was traditionally used, instead of olive oil.
In a bowl, beat the egg yolks with the sugar: they should become almost white when beaten correctly. Add the yoghurt and, a little at a time, stirring continuously, the sifted flour and baking powder, the juice and grated rind of the orange, and lastly the olive oil. Beat the egg whites until “stiff” and, taking care not to deflate them, add them to the mixture by folding them in from the bottom upwards. Grease with oil a rectangular baking tin (ideally non-stick and fairly shallow) measuring approximately 35 x 25 cm. Pour in the cake mixture, level it, and cook in a preheated oven at roughly 130 °C for a good half an hour. If the surface of the cake should begin to brown too much, cover it with a sheet of baking foil; but wait at least the first quarter of an hour of the cooking time before doing this (if you open the oven too early, the Schiacciata won’t rise properly). Remove from the baking tin while still warm. Serve the Schiacciata cold, sprinkled with icing sugar.
(1) Maria was the “baker” at La Vialla for many years: she has now retired, but her recipes continue her work for her.
(2) In Florence the present day version, found in “pasticcerie” (= cake shops), is even more “sweetened up”: with butter, instead of oil. Schiacciata Fiorentina is often filled with whipped cream or pastry-cream.