Place the pre-made pie crust in a deep-dish pie tin. Prick the bottom and sides of the dough with a fork, then bake according to package directions.
In a medium saucepan, add sugar, cornstarch, and water; whisk to combine.
Heat over medium heat until boiling, then reduce heat to low and simmer several minutes, until thickened.
Remove the pan from heat and whisk in strawberry gelatin powder.
Cool slightly, then add the sliced strawberries, stirring to coat them completely.
Pour the strawberry-gelatin mixture into the baked pie crust. Chill 2-4 hours, until set.
In a clean medium saucepan, whisk together the sugar and the cornstarch.
Add the milk and whisk until smooth.
Heat over medium heat and add the egg yolks, salt, and zest.
Bring to a simmer, stirring frequently, until thickened enough to coat the back of a spoon.
Remove the pan from the heat and whisk in the lemon juice. Allow to cool to room temperature.
Place a sheet of plastic wrap on top of the pudding (to prevent a “skin” from forming) and chill for 1-2 hours until set.
Gently fold the whipped cream into the pudding until well combined.
Pour over the set strawberries and use a spatula to spread it into an even layer.
Chill the pie in the refrigerator overnight or freeze for 2-3 hours until set.
Garnish with halved strawberries, lemon slices, and lemon zest, if desired. Refrigerate any leftovers.