How to politely turn down a lower position with a company

So...I interviewed for a position with a company that I really want to work for.A few days after the interview,I received an email saying that I didn't get the position.Honestly,I wasn't surprised.I did not think it was one of my stronger interviews.

They reached out to me today,and asked me if I would be interested in a lesser position.Financially,it's less than what I make now,but more importantly,it's a position that I am not really interested in,and not really related to the position I originally interviewed for.

What is the best way to reject this opportunity without burning bridges?I really want to work for this company,but not in this capacity.