Simply replace the unfilled areas such as "" and "[date]" with your information.
Dear [Name of Executive],
I would like to commend [full name of employee] to you. [He/She] works in our [name of employee's department] department, and recently did a superb job on the [name of project] project for us.
As you know, this was a very important project for us, and [first name of employee] really put in some quality time and work to insure an excellent end product. [First name of employee] can always be relied upon to provide us with top level work, and I feel she deserves a very heart job-well done for this recent example of her ability and work ethic.