Enchiladas aren't always hot. (Enchiladas aren't what? hot)
My friend in San Diego makes them without peppers. (Friend makes what? them)
Believe me. (Remember from Chapter 3 that the subject of a command is you, so for this sentence the question is: "You believe whom?" me)
After one bite of his enchiladas, your prejudice against Mexican food would vanish instantly. (Prejudice would vanish whom? Prejudice would vanish what? No answer, so there is no completer in this sentence.)