The dependent clause cannot make sense by itself, therefore splitting the sentence by the comma, you can determine which half of the sentence makes sense by itself. The one that doesn't make sense is the dependent clause since it is <em>dependent</em> on the other half of the sentence.
I agree it is “until you finish your homework” for me the indicating word was “until” that helped me realize that the next thing that happened depended on whether or not the first thing was completed therefore the first part of the sentence was the dependent. Hope I explained that right
