These are the most famous and best Kosher places in town:

1. Al Galope is, for locals, the most frequented Kosher Grill in town. You can order a “Parrillada”, which is a small grill they bring to your table, with the most traditional cuts of Argentine meat, heated with coals beneath the grill. The most famous Argentine cut is the “bife de chorizo” (sirloin strip stake). Al Galope is located in the Jewish neighborhood of Once, on Tucumán 2633. You can call them at +54-11-4863-6888 to place a reservation if you want to make sure you get a good table on a crowded day or night. If you go at night, please let your concierge in the hotel order a cab for you and ask the people at the restaurant to order a cab for you to take you back to the hotel. The restaurant opens at 8 PM for dinner. Please check the TripAdvisor reviews to see what people have to say about Al Galope: https://www.tripadvisor.com/Restaurant_Review-g312741-d2403064-Reviews-Al_Galope-Buenos_Aires_Capital_Federal_District.html
2. Glitter Restaurant. This is a very upscale, top-of-the-line Kosher restaurant located inside the Alvear Icon Hotel, on Aimè Painè 1130, in Puerto Madero. They are open Monday thru Thursday. They are closed on Sundays. Take a look at their web site: http://alvearicon.com/en/restaurant-bar/glitter-restaurant-puerto-madero/
3. Ioki Kosher Suhi Tucumán is also an excellent Kosher Sushi place, across from Al Galope, in the Jewish neighborhood of Once. It is located on Tucumán 2670. Call them before going to make sure they are open: +54-11-2554-8791.

For a more extended list of Kosher places, please check:
https://www.totallyjewishtravel.com/kosherrestaurants-TJ5232-Buenos_Aires_City_Argentina-Kosher_Eateries.html

For a great article on Jewish food in Buenos Aires, check here:
https://www.myjewishlearning.com/the-nosher/the-best-jewish-food-in-buenos-aires/?utm_content=bufferc3dd3&utm_medium=social&utm_source=thenosher&utm_campaign=buffer&fbclid=IwAR1-5-7LoARnbP6XiQzqNlENJWY-ZwRTGmbWkovN2_1sq8u0gytn8ZXxoaw