Preheat the oven to 350F. Prepare a 9-inch tart pan or ceramic baking dish with baking spray.

In a large bowl, whisk together the flour, sugar, coconut, baking powder, and salt. 

In a separate medium-sized bowl, stir the vanilla into the melted butter. Add to the dry ingredients. Mix by hand until evenly combined and crumbly. 

Using your fingers, press the mixture evenly into the bottom of the prepared pan, making sure not to press it up the sides. The crust should be about ½-inch thick. Poke the crust evenly all over with a fork. Bake for 15 minutes, or until golden brown, then let cool for about 15 minutes.

Meanwhile, in a large bowl, combine the sliced peaches and blueberries with the sugar, vanilla, salt, and lemon juice and mix with a spoon until combined. Let sit at room temperature to release juices.

To make the pastry cream, warm the milk, cream, lavender, and vanilla in a medium saucepan over medium heat until it begins to steam, about 4 minutes. Remove from heat and steep for at least 1 hour, or refrigerate overnight for more intense flavor. 

Set up a fine-mesh sieve or strainer over a bowl or saucepan. Pour the lavender-infused milk and cream slowly through the sieve to strain the lavender. Return the infused milk-cream mixture to the stove, add ½ cup of sugar, and bring to a light boil.

In a separate bowl, whisk the egg yolks with 1 tablespoon of sugar until smooth, then whisk in the cornstarch until smooth

Slowly pour half of the hot milk and cream mixture into the egg yolks, whisking constantly to temper them and prevent scrambling. Then, return the egg mixture to the saucepan with the remaining milk and cream. Add the salt and cook over low-medium heat, whisking continuously until the custard thickens, about 2 to 4 minutes.

Remove the saucepan from the heat and whisk in the butter until it is fully melted and incorporated. To cool the pastry cream quickly and prevent overcooking, transfer it to a heatproof bowl set over an ice bath (a larger bowl filled with ice and cold water) and stir gently as it cools. 

Spread ½ cup of the cooled pastry cream in a thin, even layer over the baked crust. Arrange the fruit on top in a pattern or scatter freely.

In a small bowl, mix the sour cream or crème fraîche with the egg yolk. Drizzle or dollop over the fruit.

Bake at 350F for 20-25 minutes, rotating halfway through, until the topping is golden and just set.

Let cool before serving. It’s best enjoyed at room temperature or chilled.