Preheat the oven to 350F (177C) convection (325F/163C conventional) and line the bottom of two 8 inch (20 cm) round pan (or three if you have them).

In a large bowl or the bowl of a stand mixer, use a whisk attachment to beat together the egg whites and granulated sugar.

Beat for a few minutes at full speed, until the meringue is fluffy and holds stiff peaks.

Add the egg yolks, melted butter and vanilla extract and beat at medium speed, just until they’re combined.

Sift the flour and salt over the batter and turn the mixer up to medium speed, just until it’s combined.

Use a rubber spatula to scrape the edge of the bowl and distribute evenly between the prepared pans, about 10 ounces each (or 6.5 ounces if making in three pans) and bake for about 20 minutes (maybe about 5 minutes less if baking in three pans). The tops should be golden brown and spring back when you gently press on the center. 

Remove the cakes from the oven and run a knife around the edge of the cake to release it from the pan. Allow it to cool for 15 minutes in the pan and then remove the cakes and place them onto a cooling rack or a tea towel. 

Allow the cake to cool completely and if desired, use a large serrated knife to slice each layer in halves or three.