Question

The applicant (who, whom, that) you recommended did not show up for the interview.​

Answer 1

When we break the sentence into clauses, we get two sentences.

We have just interviewed an applicant.The committee believes he is best suited for the position.

As you can see, the pronoun used here is he.

Hence, we should be replacing it with who.

We have just interviewed an applicant who, the committee believes, is best qualified for the position.

You can also think of it as, "An applicant who is best qualified for the position."

Hope that helps clear the confusion.