My problem arose when I pasted a copy-select from an external FORMATTED source into the top of a plain note. I decided against the imported format and deleted it, but the 20-pt bold-formatted blank line remained at the top of the note. Multiple times I tried the various excellent solutions listed above, but none of them worked for me. Every attempt left a Tahoma 20-point line at the top which included bold type. I gave up. Beginning with the first correctly-formatted line near the top, I copied the entire remaining GOOD text all the way to the bottom of the note and pasted it into a NEW note. Works okay. No unwanted formatting.
This remains a frustrating defect in Evernote. I love Evernote. Please fix the problem.