In a large bowl with a hand mixer set on high, beat the 4 egg whites until soft peaks form, about 1 1/2 minutes. Add the remaining sugar and continue beating until stiff peaks form, about 1 minute more. Fold the egg whites into the batter, then pour it onto the prepared baking sheet. Use a spatula to spread
it evenly. Bake until the top of the cake is light brown, about 15 minutes. Let cool.