Paleo friendly banana upside-down cake

Yesterday we went for a small libertarian meetup that took form of a barbecue party. As libertarians often follow paleo diet, of course I had to bake something. With fresh bananas in the house, and after spending 2 nights making a big wristwatch-shaped birthday cake with a lot of fondant work, I decided for something really simple - upside-down banana cake. 

It's as tasty as it's simple, and it was really refreshing especially during yesterday's hot evening when taken out of the fridge. It would work great with spoon of your favorite ice cream!

Ingredients
3-4 small bananas
your favorite kind of sweetener - I used 2 sticks of stevia (optional)
cinnamon
coconut oil to grease the pan
nuts (optional)

3 smaller eggs
1/3 cup of coconut cream
3 tbsp of honey or maple syrup (optional)
1/2 tbsp of baking soda
1 tbsp of cream of tartar
1.5 banana, mashed
1 cup of almond flour

1. Do not preheat oven now. I still don't understand why all the recipes start with this. Even the cheapest ovens are able to get the desired temperature in 3-5 minutes. Save the energy - it's good for environment* and your pocket as well.
2. Grease your baking tray (18x28 cm or 7x11 in) with coconut oil. Cut parchment paper to cover the bottom of your tray, put it in and grease the top again. Don't forget the sides too.
3. Sprinkle/drop your sweetener over the parchment paper. Sprinkle cinnamon as well.
4. Cut bananas to ~3mm slices and cover the cinnamon layer. You can add nuts if you like.
5. Whisk egg whites. Gradually add egg yolks, coconut cream and your preferred sweetener. Mash banana and add to the mixture. 
6. Now you can turn the oven on, to 160 degrees.
7. Mix 1 cup of almond flour with baking soda and cream of tartar (or use baking powder) and mix with the rest.
8. Distribute the batter all over the bananas. By this time your oven will be nicely preheated and you can put it in for 25-30 minutes.
9. When done, let the cake cool down, with plastic knife make sure that it does not stick to the sides and turn it upside-down to a prepared tray or board. 
10. Cut and serve and enjoy.

As mentioned, this moist banana cake is especially nice when cooled. I'm definitely going to try it out with pears as well.

*You know, the cheapest and most environmentally friendly is the energy that we stop wasting.