1Preheat oven to 400 degrees. Very generously grease a 1 1/2 quart souffle dish or an 8-inch baking dish with extra butter. Whisk cornmeal and 3/4 cup of milk in a small bowl until combined and set aside.
2Melt butter in a large, heavy pot over medium-high heat. Cook corn until beginning to brown, about 10 mins. Stir in sugar, salt, cayenne, and remaining 2 cups milk and bring to a boil. Remove from heat, cover and let mixture steep for 15 mins.
3Transfer to blender or food processor and puree until smooth. Bring the pot back to a boil, reduce heat to low and add the cornmeal-milk mixture, whisking constantly un til thickened, about 2-3 mins. Transfer to a large bowl to cool faster.
4Once cool, whisk in egg yolks. Beat egg whites and cream of tartar in a medium bowl until stiff peaks form and fold into corn mixture, 1/3 at a time. Pour batter into prepared dish and bake until golden and has risen above the rim of the dish. About 45 mins.