"Are you making tea?"
there is a difference between "robić" and "zrobić". Let's look at these two sentences in the past tense: Ja robiłem herbatę - I was making tea - durative aspect Ja zrobiłem herbatę - I made tea - perfective aspect
The first one focus on the action and it implies that there was an action of making tea. The second one implies that the tea is already done.