Start by putting the butter for the cake into a pan over medium heat. Preheat oven to 350F.

Grind erythritol for the cake in a spice grinder until powdered completely. Let settle before removing lid.

Add almond flour, powdered erythritol, psyllium husk powder, poppy seeds and baking powder into a bowl.

In a separate bowl, mix together eggs, sour cream, lemon zest, vanilla extract and liquid stevia.

Keep an eye on your butter until it browns; it should look a deep golden color.

Slowly pour the browned butter into the wet ingredients while mixing with your spoon.

Add dry ingredients a little bit at a time while mixing until your batter forms.

Grease a round cake pan, then press your batter into the pan.

Bake for 20-25 minutes, until the cake is golden brown on the top.

Let the cake cool slightly, then remove from the pan and let cool on a cooling rack.

Grind remaining erythritol in a spice grinder, then grind blackberries until a paste is formed (you can use a food processor for this, or your spice grinder if you immediately clean it out). Strain the paste into a separate container, making sure no seeds get through.

Add lemon juice and powdered erythritol to the blackberry puree and mix together well.

In a separate bowl (or clean out one of the bowls you used earlier), beat together remaining butter with heavy cream using a hand mixer.

Slowly mix in the blackberry puree until a thick icing is formed.

Plop the icing on the cake and cover the entire cake, sides included.

Place in the refrigerator for 20-30 minutes, then serve!