Aussehen is a separable verb. In the present tense the prefix (aus) comes off and goes to the end of the phrase and the base verb (sehen)then behaves as normal. It's the first one that I've seen used on here but you can bet your bottom dollar that it won't be the last. Good luck!
DO NOT TAKE THIS AS FACT. This is purely what I, as a noob see. Its almost making it relevant to the recipient. As in it almost makes it mean "you are looking good" whereas the literal translation without the aus makes it almost as if its a complement to the way the recipient sees, as in "you are excellent at looking" I repeat though, utter speculation, but ive noticed that it kinda fits
I thought "siehst" meant "see", referring to a person's vision. (example: "Du siehst die Morgenröte" means "You see the dawn".) Referring to the fact that someone's eyes are capable of seeing it.
Does it also mean "appear", referring to a person's attractiveness? This would reflect not on the person's sight, but on the sight of the people around them.
It would be the English difference between "You see well" and "You look good". One is a factual statement about my vision, the other is an opinion someone else has made about my appearance.
Are both correct with "Du siehst"...?