After rewriting someone else's blog post and passing a plagiarism checker as 100% unique, do I still need to cite my source if I want to post it on my own blog?
Just because you re-write something, doesn't make it original or YOUR work. It would be no different than handing in an essay for class that a friend let you copy off of, and all you did was change up the wording. 9/10 times the teacher will pull you both to the side to talk about why both your essays are pretty much the same thing. This is no different in the professional or blogging world either.
This might sound a tad harsh, but don't be lazy and rewrite other people's ideas and think you can take all the credit. You can write your own UNIQUE blog post that explains the topic, and reference this blog as your source. What did you like about it that made you want to re-write it? What did you not like about it or find false that made you want to re-write it? Quote parts that you liked, didn't like, and then back it up with your own original writing and research.