Put coffee and flax seeds flour in a large bowl, combine using a whisk and set aside. In another bowl add the flour, baking powder and bycarbonate.
Add sugar into coffee and flax seeds and mix well. Add oil too and whisk until you get an homogeneous mixture.
Add now dry ingredients into liquids using a sieve, little by little. Mix with the whisk to get a smooth cake batter.
Add hot water and whisk, then pour the batter into a 7 inch chiffon cake pan, slightly oiled and floured.
Bake at 340°F for 1 hour and 20 minutes. Let the cake cool down in the pan before leaving and serving.