Crust: pulse the buckwheat groats until fine. Pour into a medium sized bowl.
Pulse the dates until fine and combine with the desiccated coconut. Mix well.
Line the cake tin with baking paper. Pour the dough and press it evenly. Place in the freezer while preparing the lemon filling.
Lemon filling: blend all ingredients to a fine cream. Use a high-speed blender for best results.
Take the cake tin out of the freezer and pour the lemon filling it. Spread evenly and put the cake tin back into the freezer while preparing the raspberry layer.
Raspberry layer: mix all ingredients to a fine cream. Take the cake tin out of the freezer and pour the raspberry layer on top. Spread evenly. Sprinkle with garnish if desired. Put back in the freezer until firm.