Preheat oven to 350 degrees F. Line an 8×8 pan with parchment paper and set aside.
In a small bowl, stir together the flour, coconut oil, and powdered sugar until the dough comes together (I used a fork and then my fingers). Press into the bottom of the greased pan and bake for 7-9 minutes, until the edges are golden brown. You don’t want to over bake the crust, or it will become too hard after you add the filling. Set aside.
In a medium bowl with a handheld mixer, beat together the banana, grapefruit juice, grapefruit zest, sugar, vanilla extract, cornstarch, and flour until fairly smooth and combined.
Bake for 30 minutes, until filling it set. Allow to cool and refrigerate for at least 2 hours to completely cool and set.
Dust with powdered sugar before serving. Enjoy!!!
Keep leftovers in an airtight container and in the refrigerator.