Separate the egg yolks from the whites. Beat the egg whites with a pinch of salt until stiff peaks form.

Combine the yolks with the sugar and vanilla extract. Beat with an electric mixer until the mixture is pale and has increased in volume.

Gently fold everything together with a spatula or spoon, being careful not to deflate the mixture.

Sift the flour and baking powder, then gradually fold them in, along with the grated orange zest, mixing gently.

Line a baking sheet with parchment paper. Pour the batter onto the sheet and spread it evenly to cover the surface.

Spread the pastry cream evenly over the cake, leaving out the edges that are more browned or dry, which you'll trim off later.

You can finish it by dusting with powdered sugar, brushing with a little syrup and sprinkling with granulated sugar before caramelizing with a kitchen torch, or spreading a little reserved pastry cream on top.

Chill in the refrigerator until shortly before serving.