Preheat the oven to 375°. Grease and flour an 11-inch round fluted baking pan.
Break the eggs into a large mixing bowl and add the sugar. Use an electric mixer to beat the eggs and sugar together until the egg mixture has become very thick and turned a very pale yellow.
Sift the flour and baking powder together. Use a large spoon or spatula to fold the flour into the egg mixture, one third at a time.
Pour the sponge mixture into the prepared flan dish. Use a spatula to spread it evenly.
Bake for 25 minutes until the top is golden brown.
Meanwhile, whip the heavy cream until soft peaks form.
Cool for 2 minutes before inverting on a wire tray to cool completely.
Decorate with freshly whipped cream and fruit.