Shortbread: Preheat oven to 350°F. Line a 9x13” pan with parchment paper.
Place butter, flours, salt and powdered sugar in the bowl of a stand mixer fitted with the paddle attachment and mix until smooth.
Place shortbread dough in the prepared pan and press using your fingers to a form a layer. Refrigerate for 30 minutes.
Bake for 25 minutes, until slightly golden brown. Set aside to cool.
Poaching Rhubarb: Slice rhubarb into 4-inch pieces. Set aside.
Stir together sugar and water in a medium saucepan. Add vanilla and lemon juice, and bring to a boil, stirring until sugar has dissolved. Add rhubarb to poaching liquid, reduce heat to simmer and cook for 5 minutes. Using a slotted spoon, transfer rhubarb to a plate to cool.
In a bowl whip together the ricotta and honey. Spread evenly on cooled shortbread. Top with cooled, poached rhubarb and line the length of the shortbread. Chill for 10 minutes before slicing and serve.