Preheat oven to 350°F (175°C). Grease a 9-inch tart pan with a removable bottom.
Mix almond flour, sugar, and salt. Add melted butter and egg; stir into a soft dough. Press evenly into the tart pan. Prick the base with a fork.
Bake 12 to 15 minutes until edges are golden. Cool completely.
Heat milk in a saucepan over medium heat until steaming.
Whisk egg yolks, sugar, and cornstarch in a bowl until smooth. Slowly pour in warm milk, whisking constantly.
Return mixture to saucepan. Stir over medium heat 4 to 6 minutes until thickened.
Off heat, stir in vanilla and butter. Transfer to a bowl, press plastic wrap onto the surface, and refrigerate at least 2 hours.
Spread chilled custard into the cooled tart shell. Arrange strawberry slices on top.
Warm jam and water in a small saucepan; brush over strawberries to glaze. Refrigerate 30 minutes before slicing.