I was pleasantly surprised that Nigella Lawson has a GF, DF recipe for chocolate cake, seeing she is the queen indulgence and full-fat everything. I did not put dark chocolate in my batter, I thought it was sweet enough. A lovely dense cake with gooey icing. Instead of chia seeds you could also make flaxseed 'eggs' - 6 Tbs flaxseed soaked in about 15 Tbs water).

2 oranges
6 chia 'eggs' (6 Tbs chia seeds soaked in 18 Tbs water)
1 tsp baking powder
1/2 tsp baking soda
2 c almond meal (or hazelnut meal)
1/2 c cacao or cocoa powder
1 c brown sugar (or coconut sugar)
1/2 tsp cinnamon

Chocolate ganache:
Mix together 6 Tbs cacao powder, 6 Tbs rice malt syrup, pinch salt and 2 Tbs coconut oil until smooth

Put oranges in a small saucepan, cover with water and bring to the boil. Simmer for 2 hours. Drain oranges and allow to cool, then cut in half and remove pips.
Meanwhile, soak chia seeds in the water. 
Preheat oven to 180C and line a 23 cm cake tin with baking paper.
Blitz oranges in a food processor (skin, pith and all). Add rest of ingredients and blitz well. Scrape batter into cake tin and spread evenly. Bake for 40-50 min until cooked through.
Cool cake in the tin then turn out onto a plate. Spread with chocolate ganache and decorate with orange zest strips.