誰がこのケーキを作ったのですか。

who

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

this (something or someone close to the speaker (including the speaker), or ideas expressed by the speaker)

cake

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to make; to produce; to manufacture; to build; to construct; to prepare (food); to brew (alcohol); to raise; to grow; to cultivate; to train; to till; to draw up (a document); to make out; to prepare; to write; to create (an artistic work, etc.); to compose; to coin (a phrase); to organize; to organise; to establish; to found; to have (a child); to make up (one's face, etc.); to fabricate (an excuse, etc.); to form (a line, etc.); to set (a record); to commit (a sin, etc.)

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question

be; is

indicates a question (sometimes rhetorical); or; whether or not; some- (e.g. something, someone); indicates doubt, uncertainty, etc.; emphatic prefix; suffix forming adjectives or adverbs; in that way