Preheat oven to 180°C. Grease a cake tin and line base with parchment paper.
Mix the chia seeds and water together in a small bowl and let it sit for 10 - 15 minutes until the mixture becomes gel.
Finely shred peel of 1 orange. Juice both oranges. Combine peel, juice, ½ cup sugar, cinnamon and ½ cup water in a saucepan over medium heat. Stir until sugar has dissolved. Bring to the boil. Simmer for 8 minutes.
Puree dates with ¼ cup syrup until smooth. Beat butter and remaining sugar until fluffy. Add chia seeds. Beat in date paste. Sift flour and cocoa together. Gently fold into butter mixture with almond meal. Spoon into pan. Smooth surface. Top with orange slices, overlapping slightly.
Bake for 1 hour or until a skewer inserted into the center comes out clean. Cool in pan for 10 minutes. Meanwhile, simmer the remaining syrup over medium heat for 5 minutes or until thickened slightly. Serve the cake drizzled with syrup. Enjoy!