Buckwheat isn't a grain but I don't think it's Primal-approved. It's a pseudo-grain. If you properly soak it before eating it, it helps reduce the negative effects. But you should run it by your doc first. Likely answer will be to avoid it while on elimination.
I like Julian Bakery's low carb paleo bread, the coconut one. However, it has psyllium in it, so run that by your doctor too. Psyllium is a known gut irritant for some people. Check out chowstalker.com and dessertstalker.com for paleo baked goods. Also fastpaleo.com