Preheat the oven to 350 degrees f (177 degrees c). line the bottom of 2 9" round springform pans with parchment paper.
In a large bowl, beat together the sweetener and butter, until fluffy
Beat in the eggs, one at a time. stir in the vanilla, sour cream, almond milk, and vinegar first to prevent splashing, then beat to incorporate
Reduce mixer speed to low and beat in the almond flour, 1/2 cup (56 g) at a time. beat in cocoa powder and baking soda, until the batter is smooth. beat in the beet root powder, if using, one teaspoon at a time to reach our desired color
Divide dough among the 2 pans and smooth the top with a spatula. bake for about 25 minutes, until an inserted toothpick comes out clean. cool completely in the pans, then run a knife along the sides and flip to release
Make the keto cream cheese frosting according to the instructions here
Place one layer of cake onto a cake stand or platter. frost the top with 3/4 cup (255 g) frosting. place the second layer on top and frost the top with another 3/4 cup frosting (255 g). finally, frost the sides with 1 1/2 cups (510 g) frosting. if desired, top with chopped pecans