Directions

Crust

• Preheat the oven to 350 degrees.
• Combine flour, cardamom, brown sugar, and salt together in a bowl. Add melted butter and stir with a spatula until a consistent, crumbly dough forms. Using your hands, press the dough into a 9-inch tart pan with removable bottom, paying special attention to ensure dough rises along the fluted sides of the pan with a nice angle at the crease. Press and smooth dough with your hands to an even thickness.
• Bake on the middle rack until the top edges of the crust turn golden brown and firm to touch, 25 to 30 minutes.
• Remove the tart from the oven and let it cool to room temperature. (Once cool, you can cover it with plastic wrap and store at room temperature until tomorrow if you are making ahead.)

Rhubarb Compote

• Place the chopped rhubarb, sugar, orange zest, and water in a medium saucepan and bring it to a boil, stirring enough to dissolve the sugar. Reduce the heat to medium-low and cook until the rhubarb is broken down and soft, stirring occasionally.  
• When the rhubarb is done, taste it and if it is too tart for your taste add more sugar until the desired sweetness is reached.
• Transfer rhubarb compote into a bowl and allow it to cool to room temperature before making the tart. (If making the tart the next day, store the rhubarb compote in the refrigerator.)

Mascarpone Filling

• Combine mascarpone, honey, and vanilla in a medium bowl.  Mix with a handheld mixer on medium-high speed until smooth and the honey is well combined with the mascarpone.
• Slowly stream in the heavy whipping cream. Increase the speed to medium-high and beat until thick and you see soft peaks. 

Assemble

• Evenly spread about 2/3-cup of the rhubarb compote on top of the tart crust, followed by all of the whipped mascarpone, then the remaining rhubarb compote.  Go gently with each layer so as not to disturb the layer below it.
• Sprinkle chopped pistachios on top.
• Store in the refrigerator.  Best within two days, after which crust begins to soften (but that never stopped me!).