Preheat the oven to gas 4 / 180C / 350°F. Grease and flour two 9-inch cake pans. Remember to use metal utensils to avoid beetroot juice stains

Add the salt & cocoa to the flour and set aside. Cream together the butter and sugar until pale and light. If using eggs, add them one at a time to this mixture, beating at least one minute after each addition, otherwise just beat in the flaxseed / oil mixture

Add the beetroot juice and vanilla to the buttermilk. Alternate adding this liquid and the flour mixture to the creamed sugar. Use a spatula or put your mixer on low, don't overbeat

Put the vinegar in a small bowl and add the baking soda. It will foam up briefly. Fold into the cake batter gently, don't beat or overmix. The batter should be somewhat thick but pourable. If you think it's too thick add a little water before you add the vinegar mixture

Pour the batter into the prepared cake tins and bake for approximately 30 minutes. Allow the cakes to cool for 10 minutes before removing from the tins. Turn out and let cake cool completely on a wire rack before frosting. Cut each layer in half to create a four-layer cake if you like