Preheat your oven to 190°C (375°F) or Gas Mark 5.

Roll out the sweet shortcrust pastry on a floured surface until about 3mm thick, line the flan tins, and prick the base with a fork.

Bake blind for 10 minutes with weights, then remove weights, brush with egg yolk, and bake for an additional 15 minutes until golden brown.

In a saucepan, combine rhubarb, 7 tbsp of caster sugar, lemon juice, and zest over medium heat and cook until softened (5-7 minutes).

Mix cornflour with 4 tbsp of water until smooth, then stir into warm rhubarb and bring to a gentle boil, cooking until thickened (around 2 minutes).

Pour the rhubarb mixture into the baked pastry cases, spreading evenly.

Whisk egg whites until stiff peaks form, then gradually add remaining caster sugar, whisking until glossy.

Pipe meringue over the rhubarb filling and bake for about 20 minutes until the meringue is lightly golden-brown.