Preheat grill to medium-high heat. Tip– I recommend keeping the side with the corn slightly cooler than the side with the zucchini and red onion.: As the grill warms, notice the smell of clean heat and a faint metallic tang from the grates, a good sign they are ready. This tiered heat approach helps the corn develop even char without scorching, while the zucchini and red onion can take the higher temperature needed to get tenderness and sear. If you skip preheating, food will stick and you will not get proper caramelization, so be patient and ensure the grates are hot before adding ingredients. Check for steady glowing coals or a consistent gas flame rather than isolated hotspots.
Add the corn to a large plate and evenly drizzle the corn with about 4 tablespoons olive oil, and rub it in evenly over the corn.: When you oil the corn , feel the cool slickness under your fingers, then watch as the surface turns shiny and ready for the grill. The oil promotes even browning and reduces sticking, producing those desirable charred kernels. Rub thoroughly so all sides are coated, and avoid using too much oil which can drip and cause flare ups. If the oil pools, dab it with a paper towel before grilling.
To a grill basket, add the zucchini, red onions, evenly drizzle with about 4 tablespoons olive oil, and toss with your hands to coat evenly.: Tossing by hand lets you feel for even coverage and the warm scent of oil meeting fresh vegetables. The oil helps the zucchini and red onion sear and develop color in the basket, and the basket prevents smaller pieces from falling through the grates. An overly crowded basket steams instead of chars, so give pieces room and shake or stir every few minutes. If pieces cling together, separate them with tongs to promote even contact with heat.
Place the corn on the grill on the cooler side and grill for about 7 to 8 minutes, turning the ears every minute or two by one-quarter turn, or as needed so that corn is cooking evenly and isn’t burning.: As the corn cooks, the smell will shift to a sweet, toasty aroma and you will see golden brown and black flecks appear. Turning frequently encourages uniform charring and prevents one side from burning; aim for even, patchy color rather than continuous black. If you leave ears in one spot too long, kernels can blister and dry out, so keep the rhythm of turning to avoid scorching. Also watch for flare ups from oil drips and move ears briefly to a cooler spot if flames intensify.
Place the grill basket next to the corn on the warmer side, and toss the zucchini and red onion in the basket every few minutes to ensure even cooking. I find that they will take a few minutes longer to cook than the corn but grills vary widely so cook until all components are done to your liking.: You should hear a steady sizzle as the zucchini and red onion hit the hot basket, and visually they will develop translucent edges and browned surfaces. Turning keeps pieces from sticking and creates patchy, caramelized spots that add depth. Avoid leaving them untouched for long periods, which can cause one side to crisp excessively while others remain underdone. If pieces are browning too fast, move the basket to a slightly cooler zone to finish through.
After the corn is cooked, cut the corn off the ears with a sharp knife and place into a large bowl. Tip– If you have rubber kitchen gloves, use them as heat protection for your hands or hold the tip of the corn with a pot holder. You want to start shaving the ears when the corn is still fairly warm so the butter will melt.: When you shave the kernels, you will see the sweet juices collect in the bowl and smell a warm, roasted sweetness. Cutting while warm helps the melted butter integrate smoothly and coat each kernel. Beware of a dull knife which can crush kernels instead of slicing them cleanly; use a sharp chef knife and a secure, steady hand. If the cob slips, stabilize it against a cutting board edge to avoid accidents.
Add the butter cubes to the bowl and stir to combine.: As the warm kernels meet the butter , you will hear a soft sizzle and see the cubes begin to gloss over into a silky coat. The butter binds with the corn juices, creating a luscious mouthfeel that carries flavors through the salad. Stir gently so the melted butter emulsifies with the juices rather than pooling at the bottom. A common pitfall is adding cold butter to cold ingredients, which will not melt well; ensure the corn is warm enough for proper incorporation.
Add the zucchini, red onions, black beans, green chiles, lime juice, cilantro, salt, pepper, optional chile flakes, and stir to combine.: At this stage various aromas will mingle: citrusy brightness from the lime juice , herb fragrance from the cilantro , and the warm umami from the black beans and green chiles . Stirring integrates textures and disperses seasoning so each bite is balanced. Taste as you go and adjust slowly, because it is easier to add than to remove seasoning. One mistake is over mixing vigorously which can break down the beans, so fold gently to keep the beans intact.
Taste and decide what tweaks you need to make, i. e. more salt, pepper, lime juice, cilantro, pinch of cayenne, etc.: Use your palate as the final arbiter; the right balance will burst in the mouth with sweet, salty, tangy, and smoky notes. Add small increments of adjustments and let them meld a minute before tasting again, since acid and salt evolve with time. Over seasoning is a common problem, so add conservatively. If you oversalt, a squeeze more lime juice or a few extra beans can help rebalance.
Salad can be served warm, at room temp, or chilled from the fridge.: Serving temperature changes texture and emphasis, with warm highlighting the melted butter and chilled allowing flavors to blend and mellow. When warm, the salad offers a silky, immediate comfort; when chilled, flavors settle and the salad becomes a refreshing accompaniment. If refrigerating, keep airtight and note the zucchini softens over time, which is normal. Avoid leaving at room temperature for extended periods in hot weather to prevent spoilage.