- Coat a 1½-quart soufflé dish or 8-inch square baking dish with nonstick spray.
- Mix cornmeal and ¾ cup milk in a small bowl until combined. Set aside.
- Melt butter in pot over medium-high heat. Add the corn and sauté until it starts to brown.
- Add sugar, salt, cayenne, and remaining 2 cups milk and bring to a boil. Simmer for 2 minutes, remove from heat, and then allow to cool, about 10 minutes.
- Purée until smooth using a stick mixer or blender. Bring back to a low boil and add cornmeal-milk mixture, whisking constantly until thickened, about 2−3 minutes. Remove from heat until cooled to room temperature (about 20–30 minutes).
- Preheat oven to 400 degrees.
- Add egg yolks to cooled-down mixture, stirring. In a separate bowl, beat egg whites and cream of tartar until stiff peaks form, and then fold it into the corn mixture ⅓ at a time.
- Pour batter into the prepared baking dish and bake until spoonbread is golden brown and has risen above rim of dish, about 45 minutes.
- Drizzle with melted butter and serve immediately.