Prepare the Tart Crust:

1. Make the Dough: In a large mixing bowl, combine the flour, sugar, and a pinch of salt. Add the cold, cubed butter and use your fingers or a pastry cutter to work the butter into the flour until it resembles coarse crumbs. Add the egg yolk and 2 tablespoons of ice-cold water. Stir until the dough begins to come together. If the dough feels too dry, add another tablespoon of water until it forms a dough.
2. Chill the Dough: Wrap the dough in plastic wrap and refrigerate it for at least 30 minutes to firm up, which will make it easier to roll out.
3. Roll the Dough: Once chilled, roll the dough on a lightly floured surface until it’s about 1/8-inch thick. Gently press it into a 9-inch tart pan with a removable bottom, making sure the dough reaches up the sides of the pan.
4. Bake the Crust: Preheat your oven to 375°F (190°C). Place parchment paper over the dough and fill with pie weights or dried beans. Bake for 15-20 minutes or until the edges are golden. Remove the parchment paper and weights, then bake for another 5 minutes to fully crisp up the bottom. Let it cool completely before adding the custard filling.

Make the Custard Filling:

5. Heat the Milk: In a medium saucepan, heat the milk over medium heat until it just begins to simmer. Stir occasionally to avoid burning.
6. Whisk the Egg Yolks and Sugar: In a bowl, whisk together the egg yolks, sugar, and cornstarch until smooth and pale.
7. Temper the Eggs: Slowly pour the hot milk into the egg mixture while whisking constantly to temper the eggs (this prevents them from scrambling). Once combined, return the mixture to the saucepan.
8. Cook the Custard: Cook the custard over medium heat, whisking constantly, until it thickens and comes to a boil. Continue to cook for another minute, then remove from heat.
9. Finish the Custard: Stir in the vanilla extract and butter (if using). Transfer the custard to a bowl, cover with plastic wrap, and let it cool to room temperature. Once cooled, spread it evenly into the prepared tart crust.

Assemble the Fruit Tart:

10. Arrange the Fruit: Once the custard filling is in place, arrange the fresh fruit on top in an attractive pattern. You can be creative and use a variety of fruits such as berries, kiwi, mango, or citrus slices. The more colorful, the better!
11. Glaze (optional): If you’d like to add a glossy finish to your tart, warm the apricot jam or fruit preserves with water in a small saucepan over low heat. Strain it through a fine sieve and brush it lightly over the fruit. This will give the tart a shiny appearance and help preserve the freshness of the fruit.

Chill the Tart:

12. Refrigerate: Place the assembled tart in the fridge for at least 2 hours to allow the custard to set and the flavors to meld. The tart will also be easier to slice once chilled.

Serve and Enjoy:

13. Slice and Serve: When ready to serve, remove the tart from the fridge and slice it into wedges. Enjoy it as a dessert for any special occasion or as a delightful treat after a meal.