Grease an 8” x 8” glass baking dish with olive oil (or spray with non-stick cooking spray). Set aside.
Heat water in a large saucepan over medium-high heat until almost boiling. Once water starts to form bubbles, whisk in polenta or cornmeal, stirring continually until it starts to thicken. Season with salt to taste.
Reduce heat to just below medium and cook, stirring every 4-5 minutes, until the polenta pulls away from the pan and becomes soft, about 40-45 minutes.
Remove from heat and stir in butter, if using. Transfer polenta to the prepared dish, smooth into an even layer, and refrigerate for at least 1-2 hours until firm.
Gently loosen the edges of the polenta with a butter knife or spatula. Turn the dish upside down, supporting the contents with your hand, and tap the bottom to release the polenta. Transfer to a cutting board and cut into 8 wedges.
Preheat grill pan or gas grill to medium. Spray with non-stick cooking spray. Brush both sides of each wedge with olive oil and grill until golden brown with grill marks. Flip and repeat on the other side.
Remove wedges from heat and top with your favorite toppings. A Tuscan Meat Ragu is perfect, along with shaved Pecorino Romano and chopped fresh parsley.