sheet cake       
noun [ C or U ] US uk/ˈʃiːt ˌkeɪk/ us/ˈʃiːt ˌkeɪk/
 平片式蛋糕
a sponge cake (= a light cake made from flour, butter, eggs, and sugar) that is baked in a rectangular tin
  The sheet cake was adorned in blue and red icing. 平片式蛋糕上装饰着蓝色和红色的糖衣。 
 He brought a chocolate sheet cake into the office for his birthday. 他过生日的时候带了一个巧克力平片式蛋糕去办公室。 
 - More examples
 - I made two chocolate sheet cakes.
 - Gone are the institutional sheet cakes that were once sliced and served to patients.
 - When you choose to bake a single layer sheet cake, you’ll nearly always use a 9 x 13-inch pan.