Sofrito is a paste of onion, garlic, bell pepper, and tomato cooked slowly in oil until it collapses into something closer to jam than salad. It's built as a flavor base that goes under rice, beans, and stews rather than something served on its own. The ratio it runs on is roughly two parts onion to one part each of pepper and tomato, and that ratio is what lets you scale a batch up or fix one that's gone wrong.
The ratio, and how to scale or repair it
A basic Spanish or Latin sofrito runs about two parts onion to one part each of bell pepper and tomato, by volume, with garlic at roughly a tenth of the onion — a couple of cloves per cup of chopped onion. That holds whether you're making a half-cup for one pot of rice or filling a jar to freeze. A batch that tastes flat is usually short on tomato or hasn't cooked long enough for the sugars to concentrate. One that tastes raw or sharp just hasn't spent enough time in the pan — more time fixes that, not more garlic.
Why nothing browns for the first ten minutes
Onion, pepper, and tomato are mostly water — a chopped onion runs about 90 percent water by weight. Dump that into hot oil and the water keeps the pan's surface from climbing much past 212°F (100°C) until it's gone, because that's the temperature water boils at, and boiling puts a ceiling on how hot a wet surface gets. Caramelization and the Maillard reaction, the two reactions that turn a sofrito brown and sweet, don't get going until well above that. So for the first stretch, low heat is doing exactly what it looks like: nothing dramatic, just steam leaving the pan while the vegetables soften.
That's the real argument for patience here, not tradition. Push the heat and the edges of the mix scorch bitter before the center's water has finished cooking off, because a thin layer at the surface dries out and clears 212°F long before the bulk of the vegetables do.
Where the sweetness comes from
Raw onion and garlic taste sharp because rupturing their cells releases sulfur compounds that irritate more than they satisfy — the same family of reaction that makes a cut onion sting your eyes. Heat breaks a lot of those compounds down, and once the water's gone and the pan can finally climb past 212°F, it starts caramelizing the sugars left behind in the vegetables. What tasted sharp and grassy ten minutes in tastes rounded and faintly sweet by the time the mix has darkened and gone jammy. That shift is the whole reason to cook a sofrito down instead of just tossing the same vegetables raw into a pot.
From raw vegetables to a finished sofrito
Chop the onion, pepper, and tomato to roughly the same size so they cook at the same rate, and mince the garlic separately. Sweat the onion and pepper in oil over medium-low heat for eight to ten minutes, stirring occasionally, until they've gone translucent and the raw smell has faded. Add the tomato and cook another ten to fifteen minutes, stirring more often as it thickens, until the water's cooked off and the color has shifted from bright red toward a dull brick.
Stir in the garlic for only the last two minutes. It's cut finer than the onion and holds far less water to protect it, so it burns in about the time the onion needs just to soften — going in early is the fastest way to ruin the batch. Use a generous amount of oil throughout, not a dry pan: many of the aroma compounds in onion, garlic, and pepper are fat soluble rather than water soluble, so the oil pulls them out of the vegetables and carries them into whatever the sofrito goes into next.
A finished sofrito holds together when you drag a spoon through it, smells sweet and toasted rather than sharp, and has gone from chunky pieces to something close to a loose paste.