Gather the ingredients for the tart crust: Flour, brown sugar, cardamom, kosher salt and unsalted butter

Ingredients for the Rhubarb Compote: Fresh rhubarb, sugar, orange zest and water

Combine the rhubarb compote ingredients in a saucepan and cook over medium heat

Cook the rhubarb until it is soft and completely broken down

Scrape the cooked rhubarb into a bowl and cool to room temperature

Combine the dry ingredients for the tart crust and whisk together

Add the melted butter to the dry ingredients

Mix the butter into the dry ingredients until there are no bits of flour visible.

Press the dough into the bottom and up the sides of the 9-inch tart pan.  Make sure it is even thickness

Bake the tart crust at 350 degrees F for 30 minutes until a dark golden brown and the edges are firm to the touch

Make the mascarpone filling and refrigerate until ready to make the tart

Assemble the tart elements - tart crust, rhubarb compote, mascarpone filling

Spread 1/3 cup of the rhubarb compote across the bottom of the tart shell. Add the mascarpone filling and then top with remaining rhubarb compote

Sprinkle the top with toasted pistachios, chill and then serve the tart