Preheat oven to 350 degrees F (175 degrees C). 2 8-inch cake pans with parchment paper. Spray well with avocado oil spray. Set aside.
In a large clean bowl, whip egg whites with a pinch of salt and the cream of tartar until foamy (save the yolks for "healthified" creme brule, "healthified" coconut custard, OR "healthified" ice cream).
Mix on high speed until very stiff (you will be able to put bowl upside down and the whites won't fall out).
Meanwhile, in a medium bowl, sift the sweetener, cocoa powder and collagen together and set aside.
Once the whites are stiff, gently fold in the cocoa mixture. Add your favorite extract flavor. Stir to combine.
Divide the mixture onto the prepared cake pans.
Bake for 25-30 minutes or until golden brown and cooked through.
Place the cakes into the fridge to cool. Can be frozen for up to a month.
Carefully slice the cakes in half widthwise so you have 4 cake layers.
To make the frosting. Using a hand mixer, beat the sweetener, butter, softened cream cheese in a medium-sized bowl until smooth. Add the extracts, lemon juice and salt; beat until well combined. Taste and adjust sweetness to your liking.
Place one layer of cooled cake onto a serving platter. Spread 1/3 of the frosting over the layer. Repeat with remaining layers. Frost the outside of the red velvet cake with the cream cheese frosting.