Preheat the oven to 350°F and spray an 8-inch or 5 quart baking dish with non-stick cooking spray. Set aside.

In a bowl, mix the sugar and softened butter until it looks sandy using a rubber spatula or your finger tips when mixing. Add the egg yolks and flour. Then whisk in the lemon zest, juice, and milk.

In a separate bowl, beat the egg whites until stiff peaks form about 3-5 minutes. Gently fold the egg whites into the batter. (Batter should be lumpy with the egg white mixture and the wet mixture - it should not be smooth. If you mix it too much, you won’t get the pudding and cake texture you’re looking for.) Pour the mixture into the prepared baking dish.

Bake the pudding for 40 minutes until it's set and the top is golden. Eat it warm with powdered sugar sprinkled on top. Can also serve with whipped cream or ice cream! Super delish!