Martha says: “There’s a one-ingredient upgrade you should apply for better roasted vegetables—and it’s already in your kitchen!” Martha who? Why Stewart, of course. And she knows her stuff.

Pan-roasted veggies have really gained popularity in the last few years. They’re easy to fix, the clean-up is minimal, and they’re good for us.

But if you want to serve up the BEST roasted vegetables, then add some acid. Whether it’s a squeeze of fresh lemon juice or a splash of vinegar, acid is what you need. It brings new life to any roasted vegetable by finishing the dish with something that brightens their flavor.

Why is it important? Much like salt and pepper, acids can be used to season a dish. Martha says, “They are a huge power player for creating well-balanced flavors for so many foods, especially for things that have been cooked for a significant amount of time.” Roasted vegetables are a perfect example of this. They become tender and caramelized as they cook, which brings out their natural sugars, making them sweeter and giving them a slightly more condensed flavor. And that's where acid comes into play.

But there’s a technique to applying acid the roasted vegetables. You don’t mix it into the vegetables with olive oil and other seasonings before they go into the oven. The BEST way to use acid is by tossing the finished vegetables with lemon juice or vinegar to awaken all of the flavors and aromas—plus, it helps balance out the sweetness that caramelization creates.

While the type of acid you use is completely up to you, there are two things to keep in mind:

1. It shouldn’t be too strong. First, Martha recommends choosing an acid that doesn't have an overpowering flavor, such as strongly flavored vinegar. You want a mild vinegar such as citrus—lemon and lime are always great choices; they too work with almost all vegetables.
2. It should balance the flavors of the meal. You want to consider the flavors of the rest of the meal when picking an acid. Maybe you’re making chicken piccata as your main dish—in that case, play up the lemony flavors of that dish by adding a squeeze of two of fresh lemon juice to the tray of vegetables. If you're serving the vegetables with something more hearty, like a winter stew, a splash of apple cider vinegar will do the trick. Or perhaps you've roasted peppers and onions for tacos or chicken fajitas—a few lime wedges will be perfect.

It’s also important to know how much acid to use. Martha suggests starting with about one teaspoon of acid for each tray of roasted vegetables, then add more to taste. You likely won't need more than a tablespoon or so at most, but start small and work up to that amount.

I’ll close Martha’s roasted-veggies tutorial with one more thought: “There’s no sense in adding a finishing touch if the roasted vegetables themselves aren't up to par.” So here are a few of her tips for perfect roasted vegetables.

CHECK OVEN TEMPERATURE. Somewhere between 400 and 450 degrees F will turn out veggies that are golden brown on the outside and tender on the inside. Cooking them at a lower temperature is more like baking rather than roasting them—they’ll become tender but not crisp.

DON’T OVERCROWD THE PAN. They need room to breathe. Too many, and they’ll steam rather than roast. If needed, use two rimmed sheet pans.

FORGET PARCHMENT PAPER: It impedes browning. No matter how convenient it makes clean-up, skip it and you’ll get a better end product.

FLIP THE VEGGIES ONCE OR TWICE. Let them cook undisturbed for the first half of roasting. This allows for browning and caramelizing. Then flip them once or twice after that to ensure even color on every side.

Finally, FINISH FRESH. Finish with a touch of acid once the vegetables come out of the oven, and you’re set. Prepare for applause and rave reviews!