Why You Should Avoid Cooking Red Onions If You Want Their Full Flavor

Onions are an amazing vegetable, coming in several varieties that can all be used in a staggering degree of ways. One of the most popular variants is the red onion, a beautiful jewel with a lovely sweetness and a milder bite than the others. Those three aspects are also why it's best enjoyed raw.

Because it already has a nice sweetness to it, caramelizing it through cooking is unnecessary. Plus, if you're intentionally caramelizing an onion, you should usually use sweet onions. Cooking it long enough also makes the already mild oniony bite even less oniony, so you're sacrificing that flavor to gain sweetness that you already had. Finally, red onions' beautiful color can become muted when cooked. It can even turn a sickly blue-green color if cooked with something alkaline, such as broccoli or garlic, though something acidic such as vinegar can restore and even improve its color.

This doesn't mean you can't or shouldn't cook them. It's one of the best onions for grilling, for example, making the charred bites sweeter while leaving the interiors still nicely oniony. You can also substitute them in for white onions in most recipes, or really any onion if you're in a tight spot.

The best recipes to use raw red onion in let you see the onion or they have a flavor that stronger onions would overwhelm. Raw red onion is commonly used throughout Mexican and Tex-Mex cuisine for these reasons. It's an excellent substitute for white onion on street tacos for those who dislike strong onion flavor, for example, and its bright red color contrasts beautifully with the avocado in guacamole recipes.

Raw red onions can also be key ingredients of sauces and side dishes. You can use it in the chili mayo of a shrimp sandwich for extra tang, for example, and it provides lovely contrast and flavor for a fennel salad with parsley and lemon.

Lastly, it's often the best choice for layering in burgers and other sandwiches. The flavor is mild enough so you can still taste your other toppings and sauces, plus it's pretty to look at in the cross section that happens when you're halfway through your sandwich.

If you do cook with red onion, cook it as little as possible to preserve its flavors. Grilling's benefits have been covered. Baking or roasting it for a short time is a similar way to remove some of red onion's bite and slightly boost its sweetness. This works wonders on a BBQ chicken flatbread pizza, for example, and it's a great way to make savory breads such as focaccia with asiago and thyme more complex.

Pickling red onions, making them neither raw nor cooked, is also common. The bite of the vinegar mixes perfectly with the onion's bite and sweetness. Plus, the vinegar massively boosts the color of the onion making every piece a gorgeous pink.

There are some exceptions to not cooking red onions too much, including making red onion jam to top charred burgers. Here, you caramelize red onions instead of sweet ones so the jam is a balance of savory and sweet instead of being exclusively sweet. Plus, just like with pickling, it makes the jam a treat for the eyes.