Preheat the oven to 300F.
Prepare two, 8-inch cake tins by lightly wiping the sides with some coconut oil and covering the bottom of the tins with a circle of baking paper.
Place the flour, baking powder, sugar and salt in a mixing bowl and stir until combined. Add in the vanilla extract, 100g yoghurt, coconut oil and the eggs and mix until smooth and combined.
Divide the mixture into the cake tins and bake for 25-30 minutes. The cake should be lightly golden and have a nice rise to it. To test the cake, insert a skewer or toothpick into the centre and if it comes out clean the cake is ready. Allow the cake to cool in the tin for 10 minutes then turn it our and let it cool completely on a wire rack.
To prepare the passion fruit jam: Put the passion fruit flesh into a saucepan along with the orange juice and sugar. Bring the ingredients to a boil and then simmer for 10 minutes. The mixture will thicken into a jam-like consistency. When the mixture has thickened take it off the heat. Put this aside and let it cool while you start to assemble the cake.
The cake and the jam must both be cool before being assembled with the remaining yoghurt otherwise it will melt.