Instead of leaving it raw, I think it is better to cook the rhubarb with sugar and lemon on the stovetop, and make a compote. This would cook out any bitterness in the rhubarb.
I would recommend you bake this in an 9×9 square pan or an 8″ circle pan. Any bigger would yield very thin slices.
- Instead of cornstarch + water for the egg replacement, you can use a flax egg replacement (ground flax seed + water) or commercial egg replacer.
- You can use any whole wheat flour instead of regular flour, if you want.