What to feed a baby red salamander?

well,

try "pin-head" crickets (the smallest size they come, you may have to special order thee on the internet or form a pet store). They are a decent candidate and probably the easiest to get in quantity.

The smallest red wigglers (worms) you can get; you may have to get a bunch and pick out the tiniest ones

Springtails are good (tiny white bugs in found temeperate soil everywhere) usually you have to get these from somebody who "raises" them or "get" them form outside soils.

I have had some success getting tiny salamanders to eat live blood worms or black worms (which are aquatic and so they die on land after a few minutes) its not ecconomical but you can buy a bunch, store them in the refrigerator and present a few worms at a time to the salamander (get these at any pet store which sells lots of trpoical fish) Don't get frozen or freeze=dried (these won't work) don't bother trying petco, petland or petsmart as they don't carry them live.

Also live fruit flies are available at some good pet stores (or again on the internet) try these.