Why do we cook onions first?

When you sweat the onions first, you get more flavor out of them.

Onions won’t brown if they’re in there with other things. Onions will add flavor the the rest of the dish, so they make sense to go in first.

The process of cooking the onions first changes the flavor of them, for the better. It mellows and sweetens as the sugars are coaxed out and all the mysterious chemistry happens. You know how caramelized onions taste different yet? The longer cooking process and reaching a temperature of at least 220 degrees begins a process called the Maillard Reaction. It always results in superior flavor. It translates to anything you brown before cooking. Browning, then braising that pot roast beforehand results in much deeper, complex flavors. Hope that helps.

The sulphur compounds that give raw onions their bite are volatile, meaning that they will vaporize given a chance. This happens when the flesh of the onion is exposed to air or cooked. If the onions are cooked with oil in a skillet, most of those compounds are able to vaporize into the atmosphere. But if you cook the raw onions in the presence of water, some of those vaporized sulphur compounds will react with the water to form propanal and inorganic sulphur, and these will remain in the dish, spoiling the flavor.

excellent! thank you all for your input… i now no longer feel like i’m wasting time frying onions seperately…i know now there is true purpose for the blessed little onion! :)