6ozSoft margarine, such as Stork, Pure Baking or Flora Buttery or Butter at room temperature(Don't even start if your butter is straight out the fridge. It has to be room temperature. And don't try to soften it in the microwave. This rarely goes well.)
6ozCaster Sugar
3mediumEggs - about 2oz each in weight
6ozGluten-free self raising flour (I always use Doves Freee)
1tspBaking powder
1tbspMilk, rice milk or other dairy alternative)(I'd always recommend using Rice milk. It's not as overpowering as other flavours, does a great job and fewer people have an intolerance to it.)
1Grated zest of a lemon. Save the juice for the icing!
1tspLemon extract
Butter cream icing
3ozButter
6ozIcing sugar
Lemon juice
Dairy Free 'buttercream equivalent' icing (yes, I know I've switched to metric. Hey ho, that's how my brain does this recipe).
70gFlora Buttery or other buttery tasting dairy free margarine
50g Trex or other vegetable shortening
300gIcing sugar
Lemon juice
1tbspMilk or dairy-free milk alternative e.g. rice milke
Instructions
Cake
Heat your oven to 170°C. Grease and line two 7½" cake tins.
Blend maragine and sugar food processor until well mixed, light and fluffy
Add eggs, one by one. If needs be, and a tbsp of flour with each egg to stop the mixture splitting.
Add the flour, grated lemon zest, and lemon extract.
Blend until mixed
Divide equally between the two cake tins and smooth the top
Bake for approx. 35 minutes.
Icing
With a hand mixer, mix the softened butter (or margerine and Trex) until smooth.
Add the icing sugar tablespoon by tablespoon, adding the lemon juice in after about 3 tablespoon's worth of icing sugar. Be gentle with the mixer, or you'll cover yourself and the kitchen in a cloud of white powder.
Add the milk or milk alternative as needed until your icing is at the desired consistency. If you are making the dairy free version, your icing is likely to be a little runnier, so go easy on adding the milk alternative.
Notes
Lemon juice and gluten free flours don't seem to be the best of friends. Much more reliable to use lemon extract, and to save your lemon juice to flavour the icing.