Preheat the oven to gas 4 / 180C / 350°F and grease & line 2 x 6" round cake tins
Sift the flour, baking powder and xanthan gum into a bowl. If using gluten-free flour I suggest either of my blends below
https://cookpad.com/us/recipes/338133-vickys-gluten-free-baking-powder
https://cookpad.com/us/recipes/333165-vickys-gluten-allergy-free-flour-cake-flour-mix
https://cookpad.com/us/recipes/338049-vickys-gluten-free-flour-mix-4-cakes-cookies
Mix the sugar with the wet ingredients in another bowl. When well combined stir in the baking soda
Whisk the liquid mixture gradually into the flour until you have a smooth batter. If using gluten-free flour, let the mixture sit for 10 minutes then add enough extra milk to loosen the batter to a thick pouring consistency around 30 - 60 mls / an eighth - a quarter cup
Divide evenly between the 2 tins
Bake for 25 - 30 minutes until golden, risen and the cake has pulled away from the sides of the tin
Let cool in the tin for 5 minutes before releasing and cooling fully on a wire rack
Once cooled, make the filling by beating the margarine until smooth then mixing in the icing sugar and vanilla
Spread the jam over the top of the base cake, then smooth the buttercream filling over the top of the jam
Place the other cake layer on top and dust with some extra sieved icing sugar to decorate
You can change the vanilla for any other flavouring of choice - almond, strawberry, lemon, coffee, rum..... To make chocolate cake, exchange 4 tablespoons of flour for cocoa powder
