First, an admission - he has been lurking on this site for a number of years, and all your knowledge and advice has been incredibly useful in his and her travels in the same period; particularly in North America (specifically Montreal and Vancouver). Most recently, he and she had the good fortune to spend 2 1/2 weeks in Buenos Aires, Argentina, and he decided that it was high time that he "pay" you all back by sharing our experiences. So, here goes...
We rented an apartment in San Telmo (thank you Angela, Virginie, and AirBnB!), so we generally ate breakfast there, and also made some suppers.
Since you cannot discuss Argentine food without talking about beef, he'll start there:
Best meat - Don Julio in Palermo (he - ribeye, she - tenderloin): good carmelization, well seasoned, perfectly cooked (raro, jugoso), cutable with a spoon. And as always in BA, very generous portions. Unfortunately, the rest of the meal was rather B-flat - mushy vegetable side, inattentive service, wrong dessert.
We also ate beef at: La Cabrara (Palermo, he - beef ribs, she - tenderloin) where we were surprised at all the sides that came with the beef, so ordered way too much; Gran Parilla del Plata (San Telmo, where he and she shared a ribeye - good idea ofttimes) where the sweet potato fries were terrific as well as the meat, and; Cafe Seddon (San Telmo) where he had a ribeye with excellent roasted potatoes, grilled tomatoes and arugula, and she had the pork loin with carmelized sweet potatoes (which was actually better than his beef!)
Also noteworthy, but not necessarily red meat: Terrific deep fried rabas (squid) and garlic french fires at Bar Finisterra (Palermo Soho); seviche topped guacamole and risotto cakes at Primafila, Buenos Aires Design, Recoleta; pizza fugazzetta (a porteno original of cheese and onions, but more like foccacia than Italian pizza) at El Cuartito, a BA pizza institution since the 1930's, packed, loud and fun, but be warned, one single serving fugazzetta will likely feed two. We also ordered the arugula and prosciutto, which was way too salty for us, and way too much for two to eat. We also found ourselves a couple of times at El Federal in San Telmo, probably for no greater reason that it was near our lodgings and thus a local watering hole. Avoid the food, it was noteworthy only in its mediocrity. Go anyway for the original 200 year old bar, and have a beer.
Our favorite eating experience? After doing the San Telmo street market on a Sunday, we found ourselves hot and hungry in front of Brasserie Petanque on Defensa. Fabulous lunch of confit (he - canard, she - lamb), bright, airy and lovely space, with charming service. We liked it so much we went back on our last day (he - sweetbread vol-a-vent, tarte tatin for dessert, she - black truffle risotto, hot chocolate profiteroles for dessert). Maybe we're simply unabashed francophiles...
Last words? Portions are large most everywhere, so be careful. And generally, it was our experience that restaurant meals are incredibly inexpensive, at least by North American (or, more specifically, Canadian) standards. Even our most enjoyable feeds at Petanque, including the two confits that we enjoyed with two bottles of malbec rose, cost only just over 400 pesos, or about $80 (Can or US).
I hope some of you out there in the ether will find this contribution even a little bit as helpful as I have found yours over the years. Bon appetit!