Make the meringue
Preheat the oven to gas 4, 180°C, fan 160°C. Sift together 115g plain flour and ¼ tsp salt in a bowl and set aside. In the bowl of a mixer with a whisk attachment, whisk 12 large egg whites until frothy, then add 1 tsp cream of tartar. Once the egg whites have formed soft peaks, gradually add in 280g caster sugar, a tablespoon at a time, until you have stiff, glossy peaks. Now add 1 tsp vanilla extract and the juice of 1 lemon and whisk again for 30 seconds.