Dear Professor [Name] or Supervisor [Name],
I hope this email finds you well. It's been a while since we last spoke, but I wanted to reach out to you today to ask if you would consider being a reference for me.
As you may recall, I was a student in your [Class/Project/Lab/etc.] during my [Year/Semester]. I am now applying for [Position/Program] and I believe that your reference would be a valuable asset to my application.
I particularly enjoyed [Specific aspect of the professor's class or supervision]. Your expertise in [Topic/Field] and your passion for teaching have left a lasting impression on me. I also appreciated your [Positive trait or quality of the professor].
If you would be willing to be my reference, I would be grateful if you could provide a letter of reference or participate in any reference processes required by the application. I would be happy to send you my resume or CV and any additional information you may need.
Thank you in advance for considering my request. Your support means a great deal to me and I look forward to hearing from you.
Best regards,
[Your Name]
[Your Contact Information]