Preheat the oven to 325°F Generously butter and lightly sugar eight 4-ounce ramekins.
Sift together the flour, salt, and 3 tablespoons sugar and set aside.
Combine yuzu, milk, yolks, zest and whisk together. Add the dry ingredients.
Whip egg whites until frothy, add remaining sugar and continue whisking until medium peaks form.
Gently fold the egg whites into the yolk mixture a little at a time.
Fill the ramekins with the mixture, Put the ramekins 1 inch apart in a deep baking or roasting pan. Fill the pan with enough water to come halfway up the sides of the ramekins. Cover with foil and bake for 30 minutes.