In a large glass mixing bowl, add cream cheese. Your cream cheese needs to be very soft, otherwise it will not mix into the batter properly and you will end up with little lumps of cream cheese. I recommend heating it in the microwave (cover top of bowl with paper towel because sometimes it does splatter) at 10 second intervals, until you can whisk the cream cheese to look like a smooth frosting.
Once cream cheese is whisked to a smooth state, add egg yolks. Whisk until batter is smooth. I found from my attempts that it is important to mix everything until smooth after each additional new ingredient, otherwise it will be too hard to remove the lumps later. Add in sugar and whisk until batter is smooth. Add in lemon juice and whisk until batter is smooth.
Sift cake flour into the batter. The sifting is important. If you just add it in, the flour remains clumped up (I even tried beating it with an electric mixer and it didn't smooth out the flour lumps.) However, if you sift it in, you only need to whisk a few times for it to be easily blended into the batter. I do not own a flour sifter, so I simply pour the flour into a sieve and lightly tap the sieve against my other hand (the one not holding the sieve) until all the flour is sifted through. After flour is sifted in, whisk batter until smooth.
Add in milk and gently whisk into batter until smooth.
In a clean bowl of a stand mixer, add egg whites. Make sure your eggs whites and bowl did not come into contact with any oils, otherwise the egg whites will not whip properly. Whip the egg whites on high speed until stiff peaks form.
Add the egg whites to your batter in 3 batches. After each addition, gently fold in the egg whites as you do not want to beat out all the air that you whipped into the egg whites. It's okay if the egg whites do not completely mix in. There should still be a few small lumps and streaks of egg white remaining once the egg whites are folded into the batter.
Thoroughly grease the interior of your rice cooker pot. I used a 5 1/2 cup rice cooker for this recipe. Pour batter into the pot. Close rice cooker and press "cake" function and start. If your rice cooker does not have a cake function, choose the white rice option and you may need to press for a second cycle after the first cycle finishes. Cook cake for about 40 minutes. You can open your rice cooker towards the end of cooking time to check progress of cake. The cake should be pulling away from the sides of the rice cooker, the surface should have an even cooked color and the cake should bounce back when you touch it. Cooking time will vary depending on the size of your rice cooker as well.
Place a plate on top of your rice cooker pot and carefully invert. The cake should slide down onto the plate. Place cake in the fridge for at least one hour to set and for the cheese flavor to fully develop. If you attempt to eat it right away, the cake will taste eggy and not very sweet. Once it is set, it is much sweeter and you can taste the cheese flavor. Dust with powdered sugar before serving. Store uneaten cake in fridge.