To make chia eggs, mix ground chia seeds with water and whisk until combined. Set aside.
Preheat the oven to 180C. Grease a 7" cake tin with a little coconut oil. To prevent the cake from sticking to the tin, sprinkle the bottom of the tin with 1tsp polenta and swirl it around the sides tapping off excess. Place a circle of grease proof baking paper at the bottom of the tin.
Thinly slice 1-2 oranges (reserve the orange peel) and arrange the slices at the bottom of the cake tin. Sprinkle the slices with a little coconut sugar. Set aside.
In a big mixing bowl, combine coconut sugar, polenta, ground almonds, baking powder and salt and mix well.
In a separate bowl or a jug, whisk together coconut oil, orange zest, lemon & blood orange juice & vanilla extract until all ingredients are well combined.
Pour the wet ingredients into the bowl with dry ingredients and mix well to incorporate everything together.
Gently scoop the cake mixture into the cake tin on top of the sliced oranges (make sure the orange slices are staying in place). Spread the cake mixture evenly around the tin by gently tapping the cake tin on the worktop surface.
Bake in the centre of the oven for 40-50mins. To check if the cake is baked, insert a toothpick in the centre of the cake. If it comes out clean, the cake is ready.
Whilst the cake is in the oven, prepare the syrup. Combine coconut sugar, water & reserved orange peel in a small saucepan and bring to a boil. Simmer for 3-5mins until the syrup has slightly thickened. When ready, put the syrup through a sieve to remove the orange peel.
Allow the cake to cool down for a few minutes before turning it upside down. Whilst the cake is still warm, brush the syrup over the cake with a pastry brush. If desired, cut extra slices of blood oranges & arrange them on top of the cake (it's just for the visual effect, to make it look bright & colourful).
This cake tastes best whilst still warm. If desired, add a sprinkle of roasted hazelnuts and a drizzle of maple syrup just before serving. To turn into a show stopping dessert, serve it with a big dollop of ice cream, warm custard or cream.