I enjoyed Los Danzantes in Coyoacán as well. I went for dinner and I see they have breakfast and lunch too. ETA: I just read your comment about opening times, I guess it won’t work for you on a Tuesday (and neither will La Barraca Valenciana looks like they open at 1pm 
)
Google Maps: https://maps.app.goo.gl/Dyf9SHEPEBXUgU726
I also had a very good torta for lunch at La Barraca Valenciana in Coyoacán once, they serve Spanish food and Mexican tortas as well as craft beer and are a short walk from Frida’s house.
Google Maps: https://maps.app.goo.gl/2gm9aJZGFxVxqAju5
Report with pics from both Los Danzantes and La Barraca Valenciana:
And there’s also Mariscos Mi Compa Chava as well. I’ve only been to their location in Roma Norte (report linked below) but it had some very tasty mariscos. If you’re going to Contramar for dinner though I’m guessing you might want something other than seafood for lunch. They open at 12pm though so not sure if it’s early enough for your museum visit.
Google Maps: https://maps.app.goo.gl/MMkLB9LJFyPBipnr6
