Preheat your oven to 350 degrees. Line an 8 x 8” baking dish with parchment paper on the bottom and up the sides.
To make the base, whisk together wet ingredients until smooth (or use an electric mixer), then stir dry ingredients in until well combined. Chill if necessary to form a dough (5-10 mins). Press crust into bottom of parchment paper evenly, then poke all over with a fork.
Bake crust 10-12 minutes or until lightly brown around the edges. While crust bakes, whisk together all filling ingredients in a large bowl until very smooth, set aside.
When crust is done, whisk filling mixture one last time and pour over hot crust. Lower oven temp to 325 degrees. Continue to bake another 15-18 minutes at 325, or until filling is just set in the center. Allow the pan to cool on a wire rack completely, then refrigerate at least 2 hours before serving. Refrigerating overnight works as well.
Cut cooled bars into 16 squares using a long sharp knife for neat edges. Dust with grated lemon zest or top with a dollop of coconut whipped cream and serve. Store leftovers covered in the refrigerator for up to 3 days.