Use only a product and method approved for the disposer and the surrounding sink finish. A cleaner suitable for a kettle may be incompatible with rubber parts, metal finishes or substances already in the drain.
What the observation tells you
First distinguish a surface deposit from corrosion or damaged material without scraping aggressively. Treating the visible ring does not require filling the whole grinding chamber with descaler. Never mix an acid-based cleaner with bleach or another chemical treatment.
A useful next step
Follow the separate sink and appliance care instructions where both surfaces are involved. If approved cleaning does not remove the mark, seek advice before using a stronger product.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.