In a bowl, combine flour, sugar, and salt.
Cut in cold cubed butter until mixture becomes crumbly.
Add egg yolk and cold water, mixing gently until dough forms.
Press dough evenly into a tart pan and chill for 20 minutes.
Preheat oven to 350°F (175°C). Prick the crust with a fork.
Bake crust for 15 to 18 minutes until lightly golden. Cool completely.
Beat mascarpone, heavy cream, powdered sugar, and vanilla extract until smooth and thick.
Spread mascarpone cream evenly over the cooled crust.
Arrange fresh raspberries on top of the mascarpone layer.
If desired, warm raspberry jam slightly and brush over raspberries for a glaze.
Chill tart for 30 to 60 minutes before slicing and serving cold.