Preheat the oven to 325ºF.

1. Make the Sticky Orange Topping: Place the sugar, water, scraped vanilla seeds and vanilla pod halves in a large oven-proof non-stick or cast iron skillet and set it over medium heat. A 12-inch cast iron skillet is perfect. Stir until the sugar is dissolved. Turn off the heat.
2. Remove the vanilla pod halves. Arrange the oranges in the pan. Create a design that you want for the top of your cake. If the oranges overlap a little bit, that's fine but don't make multiple layers because you want all the oranges to get saturated. If you have extra orange slices, leave them off. Turn the heat to medium-low and simmer for 15 minutes, until the oranges are softened. Realign any oranges that moved around. Remove pan from the heat.
3. Make the Cake Batter: Melt the butter in a small pan and set aside. Place eggs, sugar and vanilla a medium sized bowl and use an electric mixer to whisk for 8-10 minutes or until the mixture is thick and pale and has increased in volume.
4. Combine flour, baking powder and salt in a small bowl. Sprinkle flour mixture over the egg mixture and fold through. Next fold in the butter and almond meal.
5. Pour the mixture over the oranges and bake for 40-45 minutes. Cake is done when a skewer is inserted and comes out clean.
6. Run a knife around the edge of the cake to make sure it's not sticking to the sides of the pan. Invert the cake onto a plate and serve.