What can I use to substitute the tiger nut flour in this recipe? I have several flours: coconut, cassava, potato starch, cornstarch, almond, pecan...

I'm so worry I missed this question so long ago! I don't believe the flours that you mentioned will work in this recipe, but I have not tried them. Working with non wheat flours is all about experimentation, unless you can find a particular recipe that has already been worked out by someone else. I experimented to get the tiger nut flour to work—by replacing the matzoh meal (which has a texture similar to tiger nuts) with tiger nut flour and making some other adjustments. The flour that you mention are nothing at all like tiger nut flour in consistency or baking qualities, so I am not hopeful. I realize that passover is long over, but for next time I suggest that you search for a passover cake that meets your requirements instead of trying to substitute apples for oranges....if you get what I mean ;-). If you do not need a cake for Passover in particular, I have scads of lovely sponges and other gluten free cakes in my book, Flavor Flours. Thanks for writing, and forgive my lapse.

*Sorry, didn't have cassava flours, but have tapioca, black sesame, green bean, and mochiko flours too.