In separate bowl from mixer, mix together almond flour, (whey or coconut flour) salt, baking powder, baking soda, sifted cocoa powder, xanthan gum.
In mixer, cream butter and Swerve.
Add eggs one at a time.
Add vanilla.
Put sour cream in measuring cup. Fill with milk up to 1/2 cup mark. (I use Fairlife, which is low-carb. You can use heavy cream if desired). This makes a buttermilk.
Add food coloring to buttermilk mixture.
Add almond flour mixture to sugar/egg mixture alternating with buttermilk mixture.
Add vinegar at the end.
Mix well.
Bake immediately for 15 minutes at 350 F./ 180 C..
Cool and frost with cream cheese frosting found here.