Preheat the oven to 400° F.
Line a 9 x 13 brownie pan with parchment paper.
Place the egg whites in a large clean bowl and with an electric mixer, beat until form soft peaks. Gradually add the egg yolks, one at a time until combined.
Add the flour, vanilla extract and sugar and mix until well combined.
Spoon the mixture into the prepared pan, spreading evenly. Bake for 15 minutes or until golden.
Mean while, spread out a sheet of parchment paper or a wet towel . Turn out the cake onto the paper or wet towel . Roll up the cake loosely from one short side, with the paper inside. Let it cool.
Unroll and remove the paper. Spread the dulce de leche and sprinkle coconut flakes over the cake. Roll up and dust with powdered sugar and serve.