If you don't need water immersion protection, it would probably do well enough to heavily grease the joint. Use a thick, high temperature grease. Not, like, vaseline, which would run off at elevated temperature.
A gasket would be preferable for maintenance purposes.
If "permanent" sealing is acceptable, then an RTV silicone rubber will do. DO NOT use corrosive (acetic or amine based) formulas!
Tim