It's fine as it is.

Student or Learner
About ten minutes later, we smelt burning. I opened the oven to find my daughter's cake on fire and it was all my fault.
Is the underlined part grammatically correct? Should I add "something" between smelt and burning?
thanks for your help!
Jason
It's fine as it is.
Welcome to Using English, Kray Cherry.
Please read this extract from the Posting Guidelines:
You are welcome to answer questions posted in the Ask a Teacher forum as long as your suggestions, help, and advice reflect a good understanding of the English language. If you are not a teacher, you will need to state that clearly at the top of your post.
Thank you.
Rover
I, too, would write "I smelled something burning."
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.
This might be another AmE vs BrE difference. "Can anyone smell burning?" or "Yesterday, I smelt burning" etc are absolutely fine in BrE.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.