Directions

1. Heat oven to 350 °F. 
2. Grease the baking sheet with parchment paper thoroughly using cooking spray.
3. In a medium saucepan over low heat, mix in the rhubarb stems, strawberries, and the granulated sugar until everything is coated well enough not to stick together when you mix them up!

4. Bring mixture just under boiling point for about 4 minutes—this helps break down those rigid cells that make fruit jams so soft & mushy tasting. Cool before storing in  fridge or freezer.

5. Meanwhile, mix confectioners' sugar, salt, and flour in a food processor until combined.
6. Add butter, then pulse until coarse meal forms 10-12 times.
7. Press mixture firmly into the bottom of the prepared pan to form an even layer about one inch thick.
8. Bake 16-20 minutes or till golden around the edges, then set aside.

For the puree:

1. Puree rhubarb until very smooth in a food processor, about 1 minute. 
2. Add eggs and yolks together with ¼ cup granulated sugar before processing for 15-20 seconds more—this will help get rid of pesky lumps!
3. Add lemon zest along with 3 tablespoons of flour if desired to create your own personalized color combinations by adding red food coloring. 
4. Spread over the crust of the shortbread cookies 
5. Bake, then set for 25 to 30 minutes.
6. Proceed to cooling them on a wire rack, and then chill at least 2 hours or to a day before cutting into squares with strawberries for garnish.