Melt the butter and leave it to cool. Separate the eggs, rub the yolks with the sugar and vanilla essence. Pour the melted egg and mix, then add the flour and mix again. Add the milk one at a time and mix until smooth. Beat the egg whites with the salt powder, and then incorporate them into the yolk composite. Put the composition in the tray with parchment paper. Bake and put in the preheated oven on high heat for 50 minutes.
P.S. The tray is 20 x30