Remove border from header image in Bueno theme?

Hi! 🙂

I have read all of the posts I could find related to this topic, but didn’t find my answer. This is my site:

https://perfectlysweethandmade.wordpress.com/

And I can’t figure out how to remove the border from the header image, as I was able to with the images in posts. Is that possible? Thank you so much! 🙂