In a mixing bowl, combine the flour, softened butter, powdered sugar, and salt. Mix until crumbly. Add the egg yolk and ice water, and combine until a dough forms.

Chill and Bake

Wrap the dough in plastic wrap and refrigerate for at least 30 minutes. Preheat the oven to 350°F (175°C). Roll out the dough and fit it into a tart pan. Blind bake for 20 minutes, then remove the weights and bake for an additional 10 minutes or until golden.

Making the Lemon Filling

Prepare Filling

In a saucepan, combine the sugar, lemon juice, and lemon zest. Heat over medium until the sugar dissolves.

Add Eggs and Butter

Whisk in the eggs until well combined. Add the butter and stir until melted and smooth. Pour the filling into the baked tart crust.

Bake Filling

Bake the filled tart at 350°F (175°C) for 20 minutes until set. Allow to cool completely.

Making the Meringue

Whip Egg Whites

In a clean mixing bowl, beat the egg whites on medium speed until foamy. Gradually add the sugar, continuing to beat until stiff peaks form.

Add Cornstarch and Vanilla

Gently fold in the cornstarch and vanilla extract. Spread the meringue over the cooled lemon filling, making peaks with a spatula.

Torch the Meringue

Use a kitchen torch to brown the meringue until golden. Alternatively, broil in the oven for a few minutes, watching closely to prevent burning.

Serving

Garnish and Serve

Garnish the tart with fresh basil leaves and additional lemon zest. Slice and serve chilled.