The number one way my family (Dad, who was the cook in our family; and his mother, who owned a Southern home-cooking restaurant) prepared summer squash:
In a saucepan with a tightly-fitting lid, put about a tablespoon of butter, and one yellow onion, sliced, or very coarsely chopped. Saute the onion briefly, until it's limp, being very careful not to let the onion or butter brown. Add 1 smashed & minced garlic clove. Add a couple of cups of summer squash, large dice. Sprinkle with a little salt. Add just a pinch of sugar. Give the whole thing a stir. Add no water. Put on the lid and put the fire on low.
(Note: With yellow squash, peel it before chopping it into large dice. That takes care of the "tough skin" thing. With zucchini, I don't bother. We often make this with a mix of summer squashes.)
Keep checking your squash and stirring to be sure it's cooking evenly. There is enough water in squash that a liquid will begin to form.
In a cup or small bowl, beat one or two eggs (depending upon how much squash you have). You don't have to work really hard at it, just kind of stir them up.
When the squash is almost, but not quite, tender, take the lid off so that some of the liquid can evaporate. Then turn the fire up a bit and pour in your beaten eggs. Stir rapidly so that the egg coats the squash. You're not going for a "scrambled eggs with squash" effect; you're going for great squash that tastes terrific and nobody can really even detect the eggs. When the eggs are cooked and the squash is tender, add a generous dollop of sour cream, or some grated cheese (I love to add Laughing Cow), and put the lid back on and let it sit. After a few minutes, give it another stir and serve immediately.
This is how my grandmother fixed the squash she served at her restaurant for many, many years.
