Looking for an easy way to improve the flavor and texture of grilled vegetables, we realized we were overlooking the most obvious ingredient: the flames themselves.

Grilling vegetables isn’t new, but in Spain’s Catalonia region, they are scorched, adding the deep flavors of char and smoke. Calçotada, for example, involves burning the exterior of young wild onions (calçots). The blackened outer layer is peeled off and the onion is dipped in a romesco sauce, eaten in one big sloppy bite.

Another Spanish dish, escalivada, gave us the bold flavor—and simplicity—we were looking for. A mix of fire-roasted eggplant, red bell pepper and onion (sometimes tomato, too), this common side dish gets its name from the Catalan word escalivar, which means “to cook in the ashes.”

The vegetables are charred on the coals of a wood fire, then the skins are peeled off. Next, they're sliced and arranged on a platter with little more than a heavy glug of olive oil, a sprinkling of salt and a splash of tangy sherry vinegar. Sometimes they get a garnish of chopped herbs, such as parsley or chives.

We loved this meat-­like treatment of vegetables. But we needed to make some adjustments to streamline the process and add texture, beginning with the cooking method. Since most Americans grill over gas or briquettes, setting the vegetables directly on hot coals wasn’t an option. Instead, we prepped the grill for both direct high-heat cooking and indirect low-heat cooking.