Prepare a 32×23 baking tray by spraying with oil and lining with baking paper.
Preheat the oven to 190°C | 170°C fan | 375°F | Gas mark 5.
In a large bowl or mixer, whisk the aquafaba and cream or tartar to stiff peaks.
Next, whilst continuing to whisk, add the golden caster sugar one tablespoon at a time. Keep going until all the sugar is combined and you have a thick glossy base for a meringue.
Now, in a cup or small jug, whisk together the vegetable oil and vanilla extract. To add the extract on it's own will react to the whipped aquafaba. Pour straight into the whipped meringue and fold quickly with a silicone spatula.
In a separate bowl. Sieve together the tapioca starch, psyllium husk and self raising gluten free flour.
Now add the mixed dry ingredients in three parts, each time folding into the whipped aquafaba.
NOTE: do not worry, your lovely fluffy mixture will reduce in size by half, this is to be expected.
Scrape the genoise sponge mixture onto the baking sheet and tip the sheet to encourage the mixture to spread. Finally tease the last bit of mixture into the corners. The mixture will be very bubbly and active.
Bake for 15 minutes, it doesn't need long at all.
Remove from the oven and rest on a cooling tray for 5mins before removing from the tin.
Once cool enough, mark the sponge out into 18 rectangles (I use a pen to mark the baking paper to give me an idea of size) You need 3x rows of 6 rectangles about 4x6cm.
Cut the sponge carefully and using the lemon curd (I added mine to a piping bag to make this 100% more bearable) cover 12 of the shapes with curd, leaving 6 'tops'.
Stack your genoise lemon slices so you end up with 6 triple layer lemon slices. Dust with icing sugar to finish.TOP TIP: to get the dusted finish in the images, I gently placed the cooling rack over the sponges at a 45° angle and dusted.