I tried this recipe from Elana's Pantry for Vegan Nut Free Gluten Free Brownies and did not like it. I was surprised, actually, because most of her stuff is delicious.
I found these tasted like banana, and were bland and too smooth for my taste. I actually added salt, which I never need to do (I usually halve the salt in recipes).
Though in her defense, I skipped all of the sweeteners and replaced the sunflower butter with almond butter. I did this because my sweet tooth doesn't need sugar if the banana is there (and who keeps xylitol around, anyway?). Also, our local store doesn't sell sunflower butter without added sugar (the Trader Joe's one has cane juice in it).
Also, there aren't that many variations on the theme of cocoa, almond butter, and vanilla. But, in this vein, these from Heather Strang are far better.