When it comes to sauces like classic béchamel that rely on flour for thickening, folks who avoid gluten may wonder if they're destined never to taste them again. But there's a really good substitute for thickening without wheat flour: the very fine corn flour known as masa harina. On Chowhound, andrewtree says Bob's Red Mill makes a good one, but you can find other brands out there, especially in Latin markets.
Maybe it's because masa harina is processed with lime (a process called nixtamalization) that softens it, goodhealthgourmet says, but somehow it behaves very much like wheat flour. It even makes a beautiful roux—not even cornstarch can do that, since with cornstarch, the germ has been removed.
And something else masa harina is good for: to substitute for flour in seasoned breading for fried fish.
Discuss: Gluten Free Bechamel