Place the oil in a sauté́ pan on the stove over medium-high heat. Add the onions and cook for 3 to 5 minutes, or until they begin to soften. Turn heat down to medium-low and cook, stirring often, for about 15 to 20 minutes more, or until the onions caramelize. Cut the kernels off the ears of corn. Add the chopped kale stems to the pan and cook 3 to 5 minutes, or until they begin to soften. Add the corn kernels to the pan, stir, and raise heat to medium-high. Cook for about 3 minutes, or until the corn’s hue begins to darken.Add the kale leaves, tomatoes and garlic to the pan. Stir and cook for about 2 minutes more, or until the kale leaves have wilted. Season with salt and pepper to taste and enjoy.