In a large skillet, heat oil to med. heat, add onions and cook until they are starting to carmelize,
stirring often so as not to scorch....that heat's too high if they do !
While onions are cooking cut squash into 1/2" slices and the large ends again in half ( yellow squash)

When onions are carmelized to your taste add squash and water to cover half way up squash.
Stir together and bring back to boil, cover and reduce to simmer till squash is just past firm ( 3/4 done ) and remove cover.
Season with about a tbl. of Rusty's Rib Rub and continue cooking til the water's gone.
You are basically steaming the squash then cooking off the water to finish them.
Truth be known, I like to let the squash brown a little in the skillet just enough so it doesn't stick...

Eat Up !
and Thanks from 3 Sisters Ranch, somewhere in Texas