Preheat oven to 375°F (190°C). Line a baking sheet with parchment paper.

Roll out pie crust on parchment; transfer to sheet and crimp the edges slightly. Chill for 10 minutes.

In a bowl, whisk ricotta, mascarpone, and sugar until smooth. Add eggs one at a time, then stir in lemon zest, vanilla, and salt until fully combined.

Pour ricotta filling into the center of the crust, leaving a 2-inch border.

Gently fold the crust edges over the filling, pleating as needed to create a rustic tart shape.

Bake for 35–40 minutes, until crust is golden and filling is set but still slightly wobbly in the middle.

Cool on the parchment-lined sheet for 15 minutes, then transfer to a wire rack to cool completely.

Dust with powdered sugar before slicing and serving, if desired.