Pour the milk in a saucepan and heat over medium-low heat. Cut the vanilla pod in half, lengthwise. Add the cooking milk and stir for a couple minutes. Remove the seeds with the tip of a knife. Remove from heat cover and let brew for 15 minutes.
In the meantime, whisk the egg yolks with the sugar. Add the cornstarch and whisk again. Add the milk and pour in a saucepan. Cook the cream, stirring constantly until mixture thickens. Pour in a bowl, cover with plastic wrap directly onto surface of cream to prevent a skin from forming. Set in the fridge
Form small melon balls with a melon baller. In a pan, caramelize the honey, rum and butter. Add the melon and cook for 1-2 minutes, gently stirring the melon balls into the caramel. Make sure not to break them. Set aside.
Preheat oven to 450F
Roll out the dough. Press into a pie dish and prick the base of the tart with a fork. Line a pie dish with baking paper and add pie weights. Bake for about 25 minutes. Remove the pie weights and cook for another 3-5 minutes.
Take the cream from the fridge and spread out on the bottom of pie. Before serving, arrange the melon balls on top and decorate with crumbled pistachios. Adding the melon before serving prevents the pie to get soggy in case the melon looses more water.