Trap html button clik in master page

Hi all,
I have a master page with an html <button> with runat=server set.  When I click the button first the page load of the child pages is called, then the page load of the master page.
I want to handle the click event in the master page, but the button does not expose a click event.  It's obvious that a postback is occuring, so how can I detect a postback to my master page load on this button's click?
thx!
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