assuming you discussed with your nanny that she must only give your child very specific foods then I dont think you are wrong to be a bit upset.
However, I doubt your nanny did this knowing it would really upset you.
Maybe she had been out all morning and was in a hurry yes, but how long does it take to make scarmbled eggs or a healthy sandwich with a few bits of fruit and salad> Not any longer than it would have taken to heat up the pasta I am guessing.
I dont eat this type of pasta because it tastes too salty so I wouldnt be happy about my child having it.
So if you have given your nanny very very specific instructions then you ANBU and you need to remind her of them.
Howeverm if you have just said, only freshly prepared food, then I can see why she gave the pasta.
If you are that fussy (no offence meant) about what your child eats then give her a list of suitable lunches that are quick to prepare, and check she knows how to make them. Also, maybe a good idea to have a few things in the freezer that you have made and portioned up. That way you know you will be happy with what your child is eating.