Pre-heat oven to 350ºF.
In a blender, process zest and juice of 2 lemons, 1/2 cup sugar, 4 tablespoons butter, 2 teaspoon vanilla extract, 1/2 teaspoon turmeric, 3 egg yolks, 1/2 cup flour and 1/4 teaspoon salt.
Transfer the liquid mixture into a large bowl.
Using a mixer, whisk egg whites and 2 tablespoons sugar on medium high until stiff peaks form. Don't over beat.
Gently fold egg whites into the lemon liquid with a spatula.
Take care to not over mix, you should still see some chunks of egg whites.
Transfer to the souffle dish.
Place the souffle dish into a large dish. Fill it with hot water to cover half of the souffle dish.
Bake for 45 minutes.
Serve warm or cold.