Combine cream, butter and Erythritol in a small pan on the stove top and heat on a medium heat until just before it boils. Turn the temperature down to as low as you can and simmer very gently for a further 10 to 15 minutes. Allow to cool slightly.
Add the remaining dry ingredients into a mixing bowl and pour in the cream mixture. Add the vanilla extract, coconut oil , lemon juice and rind and mix until well combined.
Line a 20 cm x 25 cm/8 x 10" slice tray lined with baking paper and press the mixture into the pan. Refrigerate until cool. If you don't want to ice/frost the slice, you can sprinkle additional desiccated coconut on top of the slice and refrigerate.
To ice/frost the slice, cream the butter for 1 minute with a hand mixer. Add the lemon juice and confectioners sweetener and beat till creamy and light. Spread the icing/frosting mixture on top of the slice and sprinkle wirh a little coconut. Store in the fridge or freeze.
Notes
This recipe needs to be refrigerated. Because butter and coconut oil are used in it, it will soften at room temperature.Feel free to omit the sunflower seeds or pistachio, and add macadamia or almonds in their place.If you don't like your slice too lemony, adjust the amount of lemon juice to taste.