This is a very delicious Sandwich place in my neighborhood. I normally order the #5 - Bell' americano. It's a great sandwich. Also try the wonderful cookies.
For brunch, the classic dish to get is the Feijoada, but the benny is also solid (and i don't recommend a benny lightly)—you can also ask for ham and spinach together (my favorite). For dinner you can also get the same thing, or the Moqueca (shrimp stew) is incredible. Pro-tip: if you're there for breakfast on a weekday, ask for a egg and cheese (add bacon or ham or avocado) on a croissant. Not on the menu—sounds basic, tastes amazing.
This marketplace is home to tons of amazing local restaurants, shops, and vendors— from flowers, meat and cheese, wine, and a food court downstairs. There is definitely something for you here.