Start by preparing your rhubarb! Wash and dry it, then set it aside. Slice each piece into a 1 inch diamond. To make this process easy, grab a piece of thick paper/card stock and cut out a little template with each edge of the rhombus a 60 degree angle (I used a protractor photo on my phone to help with this since I did not have a true protractor). Lay this template over top of the rhubarb to guide each slice you make. A serrated knife will assist in getting clear cuts (without to manny strings). There is no need to peel the rhubarb. Try to get each piece exactly the same size, it will help with shaping! 

I recommend doing a test design on a cutting board or plate, to get the hang of how you want your tessellation to look. Begin with one central, 6-pointed "star," laying the pieces of rhubarb as outlined in the images above and video below. Build from there, creating stars next to each other going down and out. If your rhubarb is the same size, it should fit in easily. If not, no worries! Feel free to lay the rhubarb in whatever shape you enjoy.

Set your design aside while you whip up the cake base. Preheat the oven to 375 degrees F and in a large bowl, combine almond flour, oat (or all purpose) flour, baking powder, cinnamon, and salt.

In a smaller bowl, combine olive oil, brown sugar, yogurt, and flax egg. Mix wet with dry until just combined. On a parchment-lined baking sheet, spread cake mixture in a 1-inch rectangle (it will be pretty thick).

Carefully add your rhubarb design on top of the cake. Have fun with it! Drizzle a bit of olive oil over top the rhubarb to help it soften. Sprinkle candied ginger around the sides of your rhubarb design. Bake for 35-45 minutes, until cooked through. Watch to ensure the edges do not burn. Remove from the oven and let cool before slicing.