Preheat your oven to 180°C (350°F).

Crush the Tennis biscuits into fine crumbs and mix with the melted butter until the texture resembles wet sand.

Press the mixture firmly into the base and sides of a tart dish. Bake for 8–10 minutes, then allow it to cool slightly.

In a large bowl, combine the condensed milk, lemon juice, egg yolks, and lemon zest.

Whisk until smooth and creamy. The lemon juice will naturally thicken the condensed milk mixture.

Pour the lemon mixture into the prepared biscuit crust.

Spread evenly using a spatula to create a smooth surface.

In a clean mixing bowl, beat the egg whites and cream of tartar until soft peaks form.

Gradually add the caster sugar while continuing to beat until stiff, glossy peaks develop.

Spoon or pipe the meringue over the lemon filling.

Ensure the meringue reaches the edges of the crust to seal the filling completely. Create decorative peaks using the back of a spoon.

Bake for 12–15 minutes or until the meringue becomes lightly golden brown.

Allow the tart to cool completely before refrigerating for at least 2 hours. Serve chilled.