Something like this?

(defun eval-rcf ()
  (interactive) ;; you have to do this to be able to bind it to a key or M-x it
  (save-excursion ;; this is what returns the point to where you started
    (goto-char (point-max)) ;; go to end of buffer
    (if (re-search-backward " *;; rcf" nil t) ;; search backward, don't throw an error
        (cider-eval-last-sexp) ;; the cider fn which evals the last form
      (message "No rcf found!")))) ;; if the search fails, show a message in the echo area

(define-key cider-mode-map (kbd "<f8>") #'eval-rcf)

Wow yes, that worked right away. Thanks a bunch, especially for the comments. It's very readable and straightforward.

ooooh