The hot plate (11) comprises an upper plate (61) joined to a lower plate (63) along respective sides parallel to each other. A heat transfer fluid circulation chamber (65) is defined between the upper plate (61) and the lower plate (63), with at least a first inlet (83) of the heat transfer fluid and at least a first outlet (87) of the heat transfer fluid. The lower plate (63) has two downwardly bent edges (63.2), extending along the sides of the upper plate joined to the lower plate. Stiffening ribs (79) are joined to the lower plate (63), along the heat transfer fluid circulation chamber, and to the downwardly folded edges (63.2s) of the lower plate (63).