Not really. If you plant corn, a relatively efficient crop, wall to wall, you can feed about 10,000 people who only want to eat corn all day off of a square mile of good land. That's about as dense as Chicago, which ain't exactly all high rises (though it's twice as dense as LA and 3x as dense as Portland; bet all you Portland lovers didn't realize you were living in worse sprawl than LA itself). Start throwing in some crop diversity, maybe some fruit trees or god forbid egg or dairy production, and the numbers just don't work for a city to feed itself, especially if you're going to set aside some of the land for purposes other than food production (this being a city and all). You can grow a lot of food in a city, but you still need grain crops and protein producers that eat grain crops (you're dreaming if you think everyone will just decide to be vegan) outside of the urban area providing the majority of the calories to support anything like urban density. Of course there is some potential for doing thoroughly ridiculous stuff like building farm towers as proposed above, but I don't think anyone with a serious grip on reality and the ability to use a calculator thinks something like that is practical.