The point of burning STEEM is to hopefully get a curator's attention, not just to burn the STEEM. So, you want to set a "null" beneficiary, which will actually burn the STEEM and also use the #burnsteem25 tag so that curators can find your post (only use that tag if you're burning 25% of beneficiary rewards):

When creating a post, you can use the "Advanced settings" to set a beneficiary to "null", like this:

And then add "burnsteem25" to the post as one of the first five tags.

You can learn more about it in the post Steemit Engagement Challenge Week # 4 | Propose A New Steemit Project| Steem Burn by @rosz.