The cake looks simple but is deceivingly complex with seven different layers of flavors.

deceivingly 是由动词 deceive（欺骗）加上副词后缀 -ingly 构成的副词形式。deceive 的意思是"欺骗、误导"，加上 -ingly 后表示"具有欺骗性地、表面上看似...但实际上..."。在句中强调蛋糕外表简单但实际复杂的反差效果。