Abstract: This invention relates to a closure which permits the opening of a hermetically sealed plastic container in a single action motion, which also maintains the hermetic seal under retort conditions. This closure includes a generally cylindrical side wall having threads along the inner surface thereof and a top portion having a metallic disk with its lower surface coated with a fusible coating, such as polypropylene. An annular flange is provided along the inner surface of the side wall to retain the metallic disk between the annular flange and an inwardly inclined inner surface portion of the side wall. A method is also disclosed for providing a hermetic seal on plastic containers using the closure of this invention.