A cooking appliance (1) includes a lower casing (2), a lower food-contacting heating plate (3), and an upper bell-shaped body (4) which is movably mounted on the lower casing (2) so as to be movable to and from a closed position. An upper food-contacting heating plate (5) is located inside the bell-shaped body (4) so as to be positioned, when the bell-shaped body (4) is in the closed position, over the lower heating plate (3). The upper food-contacting heating plate (5) is connected to the bell-shaped body (4) to move freely inside the bell-shaped body (4) in a direction (d0) substantially perpendicular to the reference laying plane of the upper heating plate (5). A heating-plate locking device (14) selectively impairs movement of the upper heating plate (5) in the moving direction (d0), and a control unit (9) controls the heating-plate locking device (14).