Hmm. I think it needs some gluten flour - if you don't object to using it. The flax will make things sticky, but I would fear the almond/flax mixture turning into a gooey mess. That may not actually be that bad come to think of it.

Is there no egg in the recipe? I'm also thinking that beaten egg white would help the cakey part rise to the top.

I would try 1/2 cup almond flour, 1/4 cup flax and 1/4 cup gluten flour.

You can also cut down on the amount of sweeteners and use whipping cream instead of 1/2 and 1/2.

Karen