Rhubarb Crumble Bars
You can use millet flour instead of whole wheat flour, coconut oil instead of butter, and gluten-free flour instead of all-purpose, if you'd like.
I like my rhubarb to be very tart, so you may find that you want to add a bit more sugar to make the mixture a bit sweeter. It will be hot so be careful with a taste-test.
I don't like my mixture too thick, but if you need to thicken up the rhubarb mixture, mix rhubarb with 1/2 teaspoon cornstarch before placing over crust.