To make the cake, mix the sour cream, cocoa powder, red food coloring and vanilla in a bowl.
Sift the flour, baking powder and salt in a different bowl.
Combine the buttermilk with the lemon juice and baking soda in a cup and place aside. (if you don't have buttermilk, use plain milk. Combined with lemon juice, milk turns into buttermilk)
Combine the butter, oil and sugar in a large bowl and mix with an electric mixer until creamy and double in volume.
Stir in the eggs one by one then add the food coloring mixture.
Begin folding in the flour, alternating it with the buttermilk. Begin and end with flour.
Pour the batter into 3 round baking pans lined with baking paper or greased with butter (20 up to 22cm diameter pans).
Bake each layer in the preheated oven at 330F for 30-40 minutes. I have a gas oven which doesn't keep a steady temperature so I always have to bake cakes longer than requested by the recipe. What I recommend you to do is to check the cake with a toothpick or a skewer and remove the pans from the oven when the cake is still moist. Overbaking it yields a dry, crumbly cake.
Let the cakes cool completely then level them if needed, using a sharp knife. Reserve the trims to decorate later.
Cream cheese mousse
For the cream cheese mousse, mix the gelatin with water and let it bloom for 10 minutes. Melt the gelatin a few seconds in the microwave.
Combine the cream cheese with sugar then stir in the gelatin.
Add the vanilla extract and lemon zest then fold in the whipped cream.
Place the mousse in the fridge 30-60 minutes until set then use this mousse to fill and frost the cake.
Decorate with cake crumbs.
Cream cheese frosting
To make the frosting, mix the cream cheese and butter until creamy.
Gradually stir in the sugar, ½ cup at a time then add the vanilla and lemon zest.
Turn your mixer on high speed and mix 2 minutes until fluffy.
Fill and frost the cake then decorate it with cake crumbs.
Traditionally, the cake is made with buttercream, but since I don't like buttercream I came up with that cream cheese mousse which is harder to work with and doesn't hold its shape as well as buttercream, but tastes lighter and less sweet. Feel free to use the frosting you like!
Recipe by Pastry Workshop at http://pastry-workshop.com/red-velvet-tort-catifea-rosie/