I recently bought some peanut butter powder! I've only used it in one recipe, though, so I don't have a great handle on how much it takes before you can taste it.

I feel like two tablespoons wouldn't be enough to give you a real peanut flavor, but it's not going to tank your muffins, either, so it'd be safe to try.

On the other hand, if you put a 1/4 cup in, you could either leave out a little of the almond flour or just add some extra liquid in--water, milk, whatever. The only issue is how thick the peanut powder will make the batter, and that's easily fixed.