Brunch - Sunday's
Nemo. If you are going in gentler weather, the patio is lovely but the restaurant is great inside as well. I had the best croissants here. The buffet is lovely and nary a food service type tray in sight. (I personally think many chef's leave the Sunday buffet to Sysco or Orval Kent).
Had a lovely brunch at Baleen but it's been awhile for me so I don't know how it is currently. Plan to find out in the next month though. LMF
Two places spring to mind. Casual and no buffets. The Front Porch in the Penguin Hotel on Ocean Drive, and Balans on Lincoln Road, both of them offering a full bar so you can indulge in Mimosas or Bloody Marys if you wish and both having a well-balanced menu without being frou-frou or over-the-top expensive. The cred comes from being popular with the locals.
One thing I've noticed about Miami, it's not a brunch city. We could use some more offerings.