Preheat oven to 375° F | 190°C.Roll out pie crust and lay in a shallow pie dish or tart pan. Crimp or trim edges.
Use a fork to prick a few holes in the bottom of the pastry shell.
Bake in preheated oven for 10-12 minutes. The crust should be bubbly but not yet browned. Set aside.(See Blind Baking NOTES for more info.)
Prepare Vanilla Cream
In a medium bowl, whisk together egg yolks and egg. Set aside.
In a small bowl, stir together cornstarch, sugar, and cardamom.In a heavy saucepan, add cornstarch mixture to milk and whisk to combine. Bring to a simmer over medium heat, stirring constantly, just until the mixture begins to thicken.
To avoid cooking the eggs, temper them by adding ¼ cup of the hot milk mixture to the eggs in the small bowl, one tablespoon at a time.
When the entire ¼ cup of hot milk mixture has been added to the eggs, slowly pour the egg mixture into the milk mixture in the saucepan, whisking constantly. Continue stirring until the mixture simmers and thickens.
Remove from heat. Whisk in butter and vanilla.Pour into a heat-proof container and place a piece of plastic wrap directly on the surface to prevent a skin from forming. Refrigerate 15 minutes.
Pour cooled pastry cream into prepared pie crust.
Fill a medium bowl with cold water and add 2 teaspoons of lemon juice. (Orange juice works too!)Peel the peaches. (I prefer to use a quick boiling water bath to remove the skins.) Slice the peeled peaches into thin slices.
Submerge peach slices in prepared lemon-water for a few minutes, and then remove and pat dry with paper towels.
Arrange peach slices on top of the tart, and sprinkle with two tablespoons of raw sugar.
Place tart in a 375° F | 190°C oven and bake 35-45 minutes, until the edges of the peaches are just barely turning light brown.Remove the baked tart from oven and allow to cool for about 30 minutes.
Using a mixer, blender, food processor or hand blender, puree peach preserves.Use a pastry brush to brush the pureed peach preserves over the top of the warm peaches on top of tart.
Blind Baking without Pie Weights: Generally, when blind-baking pastries, I use a circle of parchment filled with pie weights (or dried beans) to hold down the pastry as it bakes. That said, I don’t usually use pie weights for this tart because it seems to bake up fine without them.Typically when you prepare a cooked pudding or cream pie filling, you cover it with plastic wrap for the entire time that it is cooling to avoid a skin from forming on the top.However, for this tart, the skin is helpful for keeping the peaches from sinking into the tart, so do not cover it once you pour it into the crust in the tart pan.