What? Is that a typo? Nope. Pungent and sometimes acrid when raw, the onion actually does amazing things when you cook it! Ready for the chemistry lesson?
The strong smell and taste of a raw onion comes from the sulphuric compounds trapped within its cell walls. This compound is released when you cut into it, and is the reason chopping onions makes you cry! Anyway, when you heat an onion, the sulphuric compounds are released -- the longer you cook them, the sweeter they get! And I'm not just talking about the so-called "sweet" onions like Vidalia or Walla Walla. Eaten raw, these are sweeter. But even those yellow onions in the big bag will get increasingly sweeter as you cook them.
So here's my Svelte Tip: If you've over-spiced a dish -- or simply to add amazing flavor, regardless -- heat chopped onion in a bit of olive oil until it begins to "sweat." In other words, don't brown the onions on high heat, cook them until they're soft and translucent on medium/low heat. The smaller you chop them and the longer you cook them, the sweeter they will become, melting into your dishes and adding a complexity and sweetness you can't beat!