First make the Polenta: Lightly oil an 8 inch square baking pan and set aside. Bring the Water, salt, oregano and lemon zest to a boil in a medium saucepan. Slowly whisk in the cornmeal, and cook, stirring continuously until mixture is thick and starts spitting cornmeal all over the place. About 1-2 minutes. Immediately pour into prepared pan and smooth the top. Let cool for at least an hour in the fridge until firm. When you are ready to eat, unmold the polenta from the pan and cut it into small cubes. Set aside.
Heat the olive oil in a large skillet over medium heat. Add onions and cook for 3 minutes. Next add garlic, cooking and stirring for an additional 30 seconds.
Deglaze the pan with the water and add kale and olives. Cook and stir until kale has wilted, about 1-2 minutes. Lastly, add polenta cubes and tomatoes. Slightly mash the cubes and cook until heated through, about 4-5 minutes. Stir in salt and pepper and serve immediately.