KaleHOW: Sauté with a bit of olive oil.WHY: Kale is rife with polyphenols that are water soluble, so if you steam or boil it, they’ll escape into the water. Cooking it dry with an oil helps you absorb the fat-soluble carotenoids, too. (Make the most of this superfood with these 11 recipes that’ll make kale exciting again.) Purple PotatoesHOW: Season with turmeric or curry powder and bake.WHY: Boiling purple potatoes releases hard-won anthocyanins into the water; baking retains them. Adding in a phytochemical-rich seasoning like turmeric gives you a double hit.MORE: 10 Mind-Blowingly Good Baked Potato Recipes OnionsHOW: Chop into wedges, let sit for 15 minutes, and roast at 375° to 400°F for 20 minutes.WHY: When you chop an onion and let it sit, you allow an enzyme to form health-promoting sulfur compounds throughout the entire onion. Roasting preserves the phytochemicals, with the bonus of a sweet, caramelized flavor. (Try this delicious recipe for roasted vegetables.) CornHOW: Roast, then boil farmers’ market corn, potatoes, and peppers; pop them in vegetable broth with fresh herbs like thyme and basil; and make a fresh corn chowder.WHY: When you boil water-soluble phytochemicals, like those found in potatoes, corn, and peppers, they leach out. “But don’t feel bad about bolling these, because all the nutrients will be retained in the broth,” says Bolling.MORE: 12 Crazy-Good Ideas For Fresh Corn CarrotsHOW: Peel a thin layer, coat in oil, and roast.WHY: The polyacetylenes found in carrots are concentrated near the edge; peel too aggressively and you risk losing them. Polyacetylenes are lipid soluble, not water soluble, so you’re not going to lose them by bolling or steaming, but roasting tastes the best. ParsleyHOW: Make tabbouleh.WHY: Parsley is very rich in flavonoids, especially the potential cancer-fighter apigenin. “People will typically just use it as a garnish, but in tabbouleh, you can eat more than just a little,” says Bolling. PeppersHOW: Grill with oil.WHY: Grilling maximizes phytochemicals by breaking down the plant-cell walls. Add a little oil for flavor and to help your body absorb those valuable carotenoids. MORE: The Best (And Worst) Oil For Every Cooking Method