Preheat the oven to 180°C (350°F).
Place the pre-made tart shell in a tart pan.
In a saucepan, heat the milk until just simmering.
In a bowl, whisk together the egg yolk, sugar, and cornstarch.
Slowly pour the hot milk into the egg mixture while whisking continuously.
Return the mixture to the saucepan and cook until thickened, stirring constantly.
Remove from heat and stir in the vanilla extract and lemon juice.
Let the cream cool slightly, then pour it into the tart shell.
Wash and slice the strawberries, arranging them on top of the cream.
Chill the tart in the refrigerator for at least 1 hour before serving.