I'm not sure, but I know that when a family member had to do a low FODMAP diet, they couldn't eat things with onions in them. But onion infused oil was fine because the sugars in the onion were water soluble, but not fat soluble so the oil didn't contain the component they were avoiding. https://www.monashfodmap.com/blog/all-about-onion-garlic-and-infused-oils-on-the-low-fodmap-diet/

Not sure it's related but it's the first thing I thought of.

@SubArcticTundra Because the flavor goes into the water! That's why soup broth tastes good. Try chopping up half an onion, boiling for 10 minutes in a pot with enough water to cover them, then taste the water.

Steam / water doesn’t allow the temperature to get high enough.

I've never heard of sautéing them in water I just throw them straight in the pan

"saute on water"?

How's that different than steaming or boiling

Are you putting the onions in the water when steaming them, or are they properly elevated so that the rising steam is cooking them? Because, generally, boiling things or cooking them in water directly kinda mutes the flavor.

Instead of sauteing with water, use butter. Or nothing if you are confident they won't stick to the pan. Also a sprinkling of salt helps draw the moisture already in the food out and helps give it a crust.

I had a whole post typed up but my app crashed. Lol.

America's Test Kitchen has a video on this and it's pretty interesting: https://youtube.com/watch?v=rzL07v6w8AA

At 2:12 she caramelizes onions in a pan. I like ATK because they explain the science behind it.

edit: I'd suggest watching the whole video because it's pretty dang interesting. Hope this helps! :⁠-⁠)