The word cathedrals is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 17
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (36 words)
acaters, arcades, archeal, archlet, caldera, cartels, castled, cathead, chalets, charade, charted, chaster, clarets, clashed, clasher, cradles, crashed, dearths, halters, hardest, hatreds, heralds, lactase, larches, latched, latches, lathers, reclads, redacts, satchel, scarlet, scathed, slather, threads, trachea, trashed