This container comprises: an outer receptacle containing a lower vessel carrying calcium oxide, a water bag and a striker to break the bag and mix the water with the calcium oxide causing an exothermic reaction; and an upper vessel carrying the pre-cooked food and fixed on the lower vessel. The outer receptacle has on its side surface: recessed sectors and projecting sectors forming hollow side chambers between the lower container and the side surface of the outer receptacle and, in correspondence with the upper end of the mentioned vertical sectors, a perimetral step for the linear support of a projecting rim defined in the upper opening of the lower vessel. The upper vessel comprises a perimetral step in an area close to its upper end for its support and fixing by means of an adhesive on the projecting upper rim of the lower vessel.