Heat 1 tablespoon of the oil in a 4-quart Dutch oven over medium-high heat. Add onions and garlic and cook and stir for 3 to 4 minutes or until tender. Stir in broth and potatoes. Bring to boiling; reduce heat. Cover and cook for 10 to 15 minutes or until potatoes are tender. Stir in kale and oregano. Cover and cook for 2 to 3 minutes or until kale has wilted. Remove from heat. Stir in lemon zest and juice and remaining oil. Let stand 10 minutes. Season to taste with salt and pepper. Top with cheese and additional lemon zest, if desired.