Preheat oven to 325 degrees Fahrenheit. Grease an 8 X 8 inch glass baking dish.
Place egg whites in a medium bowl. Whisk to stiff peaks with an electric hand mixer. Set aside.
In a large bowl, beat egg yolks with sugar until light, about 1-2 minutes. Add butter and vanilla extract and keep beating for another minute or two . Add flour and mix until fully incorporated.
Slowly start adding the milk and beat until everything is well mixed ( can do with a regular whisk). Add the egg whites, a third at a time and fold them in using a spatula. Repeat until all egg whites are folded inches It is ok to have a bunch of white clumps.
Pour batter into greased baking dish and bake for 50-70 minutes or until top is light golden brown and cake is only a little jiggly.
Dust with confectioner's sugar after it has cooled. Serve with strawberries if desired.