Sift the flour, salt, and baking powder into a bowl. Set aside.
Using an electric mixer, beat the egg yolks, half the sugar (125 mL or ½ cup), and vanilla extract together in another bowl until pale. Add water and stir gently.
Add dry ingredients in three batches, mixing gently with a spatula between each addition. Set aside.
In another bowl, use an electric beater to beat egg whites until soft peaks form. Gradually add in remaining sugar and continue beating until stiff peaks form.
Gently fold egg white mixture into reserved cake batter with a spatula.
Divide mixture into the two 20-cm (8-in.) spring form pans. Smooth the batter on top with a spatula.
Bake on middle rack for 25 to 30 minutes, or until a toothpick inserted in the centre comes out clean. Turn upside down on wire rack to cool.
Gently remove from pans.