In a large heavy pot over medium heat, heat oil. Add fideo; season with ½ tsp. salt. Cook, mostly undisturbed, until golden brown and toasted, 2 to 3 minutes. Using a slotted spoon, transfer to a medium bowl.
In a blender, blend onion, garlic, and tomatoes until nearly smooth and mixture is light pink and aerated. Transfer to pot, being careful to avoid splatter. Cook over medium heat, stirring occasionally, until rawness of onion and garlic cook off, about 10 minutes. Stir in coriander and cumin; season with remaining ½ tsp. salt.
Add fideo and broth. Bring to a simmer over medium heat and cook, stirring occasionally, until noodles are tender, 15 to 18 minutes.
Divide soup among bowls. Top with queso fresco and cilantro. Serve with lime wedges alongside.
