How can I clean a brown rust stain that is in the toilet bowl?

https://www.hunker.com/13423330/how-to-remove-rust-from-a-toilet-bowl

Lysol Lime & Rust Remover Toilet Bowl cleaner, comes in a black squirt bottle. Scrub with Scrub Daddy or Mr. Clean Magic Eraser. If super stubborn, use an emery scrub block.

I hear your cry! I have had the same problem with very old plumbing (rental property). I got FANTASTIC results from a one-time application of LIME-A-WAY Toilet Bowl Cleaner (Thick gel formula) Fast removal of the toughest stains- LIME-CALCIUM-RUST -- use with a LOT of ventilation-- bowl must be DRY where you want to "squirt" the cleaner as in the upper UNDER edge of bowl where the water comes out...Producy is thick-- globs around, WEAR PROTECTIVE GLOVES-- it will burn your skin. Don't breathe the fumes! NOW-- other than that-- it will get rid of those stains. I was TOTALLY amazed with the outcome of only ONE application! I ended up with the brightest, white-ist bowl in town!

There is a product called Whink. It is highly caustic. You must use gloves. I’ve never seen a rust stain it could not eliminate. It also works almost instantly.

Here is what I use to clean anything in my home.. https://bushraslifestyle.com/diy-cleaning-caddy/

Hope it hleps! Bushra