Blood orange upside-down cake

I've got inspired 2 weeks ago to make a blood orange upside-down cake. I bought the oranges and waited 2 weeks to find the time to actually put the recipe in practice.
The cake actually turned to be exceptionally good and incredibly flavored. Also, not very time consuming and not over complicated.
Now I am again inspired to do all sort of upside-down cakes with all sorts of fruits. Let's see...

Ingredients:

Sirop:

• 1 cup of sugar
• 1 cup of water
• 1/2 teaspoon cinnamon
• 2 tablespoons orange blossom water

Dough & top layer:

• 3 blood organic oranges (+ more for the juice bellow)
• 650g all purpose flour
• 150g butter (melted)
• 145g sour cream
• 1 tablespoon orange zest
• 14g baking powder
• 400g fresh orange juice
• 6 eggs
• 120g sugar

Directions:

1. Slice very finely the oranges using a sharp knife or better a mandoline.
2. For the sirup, add the water and the sugar in a pan and heat it until boiling. Mix to insure that the sugar is dissolved.
3. Add the orange slices in the pan and caramelize them for 3-5 minutes.
4. Take a cake/tart pan (preferably one with a removable bottom that is not leaking) and arrange nicely the slices on the bottom of this cake pan. Put the pan aside and let's prepare the dough.
5. In the bowl of a standing mixer add the eggs and the melted butter and mix.
6. Add the sour cream, orange zest and sugar and mix.
7. Combine the flour with baking powder and add it in the mixing bowl alternating with the orange juice.
8. Pour this composition over the blood oranges in the cake pan.
9. Bake the cake for 35 minutes in the preheated oven at 180ºC.
10. When finished, let the cake to cool before reversing it from the pan.
11. Serve it dusted with icing sugar or whipped cream.