Some concepts from English can be applied to German, some can't.
In this case, your confusion is the result of the English verb form present continuous: "I am going", "You are going", "Are you going?".
This form just doesn't exist in German, so it isn't used in questions, either. So instead normal present tense is used:
Unlike English, German does not need an auxiliary verb to form a question.
German also does not have a continous form constructed using to be + present participle.
This means that there are two cases where English uses an auxiliary verb but German does not.
So it's correct that
Are you going?
Note that are, if translated, ...