Charlotte or Upside Down Apple Cake

I have not made this cake since I was a kid. In fact, I almost forgot that it exists. My mom reminded me about it when she visited me last winter. This cake is familiar to every Russian. It is so simple to make and it is so delicious I can't believe that I have not made it since I was 14. In Russia it is called Charlotte and I can call it that,  too,  or I can say it is an Upside Down Apple Cake. My mom makes it using the recipe a little bit of this and a little bit of that, so  I have measured everything out here. I made it yesterday since we were invited to a Shabbat dinner and I was requested to bring a parve dessert. Parve means that it's neither dairy or meat. I could not think of anything but Charlotte.

6 eggs separated
1 1/4 cup of sugar
1/4 teaspoon Cream of tartar
1 teaspoon vanilla extract
1 cup of flour
2 Granny Smith apples peeled and sliced
Cooking spray for spring the pan and flour for dusting it.
Prepare your apples first. Spray with cooking spray the baking pan and dust it with flour. Tap on the baking pan to remove excess flour. Separate egg yolks from egg whites. I use both my food processor and my KitchenAaid mixer for the next two steps. In the clean bowl with a whisk attachment whip up eggs whites with cream of tartar and half of the sugar, until egg whites form stiff peaks. In the food processor, mix egg yolks with the rest of the sugar until thick light yellow mixture and ribbons form when you lift the blades. Add vanilla and flour to the egg yolks and mix until well blended. The next step is important, because you must carefully fold egg yolk mixture with about about one third of whipped egg whites without deflating egg whites too much. Then carefully fold the rest of  the egg yolks and whites together. Once you have everything folded together you can fill in the cake mold pouring the cake batter over the arranged apple slices. Place in the pre-heated oven at 350 F and bake until the tooth pick inserted in the center comes out clean, or for about 50 minutes.

My mom used the same recipe when she made a birthday cake for me when I was a kid. She made it for my youngest when she visited this winter. Here are some pictures of the cake. To make it in to colors, before folding the yolks and egg whites she divided the egg yolk mixture in two, then to half of the mixture about a tablespoon of cocoa was added. This way she would have two batters one chocolate and one vanilla. The egg whites would also be divided in two and once folded together baked in separate baking pans. That way you would have to layers of the cake or four if you cut the individual cakes in two after baking. Another option is to pour the chocolate batter into the vanilla batter once it's in the baking pan, this creates a marble effect in the cake once it's baked. The icing for this cake was also quite simple. Soft and unsalted butter was whipped with sweetened condensed milk and once more adding a tablespoon of cocoa powder creates a chocolate flavor icing. Simple and very delicious just as the best childhood memory can be. "Mother knows best",-thanks for reminding me of that, Mom.