Lemon pudding cake

In a large bowl, beat together the butter, 1/2 cup sugar, and lemon zest until light and fluffy. Add in the egg yolks one at a time, beating between each addition. Mix in the flour, vanilla, and salt. Stir in the lemon juice and milk. The batter will be very runny. Set aside.

In a large mixing bowl, beat the egg whites until soft peaks form. Add in the cream of tartar and remaining 1/4 cup sugar and continue beating until stiff peaks form. Mix 1/3 of the egg whites into the cake batter until completely mixed. Fold in the remaining egg whites.

Transfer batter into the prepared baking dish (the cake will not rise so it is okay to fill the dish to the top, if necessary). Place the baking dish into a larger baking or roasting dish and add boiling water in the large dish until it reaches halfway up the outside of the batter-filled pan. Carefully transfer to the oven and bake for 50-60 minutes, or until the top becomes golden and the middle of the cake barely jiggles when shaken.

Cool the cake for 45 minutes to 1 hour before cutting or serving to allow the cake to set. Sprinkle with powdered sugar, if desired.