Ugolino da Siena, ‘The Last Supper’, ca. 1325–1330, The Metropolitan Museum of Art

overall, with engaged (modern) frame, 15 x 22 1/4 in. (38.1 x 56.5 cm); painted surface 13 1/2 x 20 3/4 in. (34.3 x 52.7 cm)
http://www.metmuseum.org/art/collection/search/459131

Image rights: The Metropolitan Museum of Art (Robert Lehman Collection, 1975), licensed under CC0 1.0 Universal