In the bowl of a stand mixer, add softened butter and sugar. Beat on medium low setting until incorporated and smooth.
Add egg and continue beating on medium/low setting until incorporated
With mixer running on low, add flour, salt and continue beating slowly until you get a grainy mixture that comes together when you press it between your fingers
Place the dough mixture into a 9-inch round tart pan (the kind with the removable bottom). With your fingers, press the mixture down and up the sides until you have full coverage. You can use the bottom of a measuring cup to help you get a nice and flat bottom and even edges.
Place tart pan in fridge for 30 minutes
Prick bottom of tart with fork. Bake for 15 minutes with pie weights (I use a mix of old beans as pie weights) on parchment paper.
After 15 minutes, check the tart shell. Edges should be starting to brown slightly. Take tart out of oven, remove pie weights and parchment, and place back in oven, drop temperature to 350F (175C) for another 10-15 minutes. Tart should be slightly brown and firm to the touch. Every oven is different, so you may need more/less time. Use your judgement.
Remove tart pan and cool completely on rack
Make Pastry Cream
In a small saucepan (off the heat), combine sugar, corn starch, flour, egg yolks, egg, and ½ cup of milk. Whisk vigorously to combine.
Add rest of the milk, cream and vanilla. Whisk to combine and turn on heat to medium. Bring to a boil while constantly whisking. Mixture will begin to thicken. Should take 8-10 minutes.
When pastry cream bubbles and thickens, drop the head to med-low and continue to cook for another 2 minutes.
Remove from heat and whisk in cold butter. Butter should be cubed into small pieces and you can add it slowly and whisk whisk whisk!
Transfer (you can sieve the mixture for a better result - optional) to Pyrex bowl, or stone dish and cover with plastic wrap. Plastic wrap should touch the cream surface so a film does not form.
Let cool on the counter for 30-60 minutes. Don't cool down completely, you still want it slightly runny.
Assemble Tart
By now, the tart shell should be cool and the pastry cream should be around room temp. Whisk the pastry cream and then pour it into the shell. With a small offset spatula, spread and level the pastry cream. Place plastic wrap on the tart and refrigerate for at least 2 hours. Now we want the cream to set.
Assemble Tart (continued) - add fruit
Now you can let your artistic side shine. Decorate the tart with peaches, strawberries, plums, blueberries, mangoes... what ever you like!
Notes
I have made this with homegrown peaches, plums and pears. I've also used strawberries, blueberries, raspberries, oranges and grapefruit. Go crazy! Make it your own!