Trim ends of eggplants and then slice lengthwise into ¼-inch thick slices. Next, in a small mixing bowl, stir 3 teaspoons of canola oil, balsamic vinegar, garlic powder, salt and cayenne pepper together. Now, brush both slides of eggplant slices generously with vinegar mixture. Heat gas grill to medium-high heat and brush grill grates lightly with remaining canola oil. Grill coated eggplant for 12-15 minutes or until black grill marks appear, flipping and brushing with remaining vinegar mixture every 3-4 minutes. Serve on a bed of grilled kale if desired.