Maybe this will be helpful: FINISHED in "you finished eating" is not the same as FINISHED in "you are finished eating". They look exactly the same, but they are in fact two different grammatical forms. FINISHED in "you finished" is preterite (compare: you drank) FINISHED in "you are finished" is past participle (compare: you are drunk) For the verb "to drink", the preterite and the past participle are different, so it's clear that you have to say "you drank", not "you drunk" and "you are drunk", not "you are drank". For the verb "to finish", the preterite and the past participle are the same. The word "finished" can have two different meanings. That's why students can easily get confused (and why a native English speaker may have difficulties understanding what the student is confused about.)

you finished eating – you did what? That's your action. You did finish what you were doing (eating). You brought your action (eating) to completion. you are finished eating – you are what? That's your current state. You are in the state where you are no longer eating. You are done with eating. "You landed" puts the emphasis on what you did – you were flying and then you descended to the ground. "You are landed" puts the emphasis on which state you are now in – you are on the ground, you are no longer flying.

"When you were finished..." indicates that this happened in the past. "When you are finished..." indicates that this is the future. Your examples are both correct and can be used interchangeably: "When you finish eating, let's go home." "When you are finished eating, let's go home." To indicate the past, it would be: "When you finished eating, did you go home?"