Preheat the oven to 350 degrees F. Generously butter a 9-by-13-inch baking dish. Sift the flour, sugar, cornmeal, baking powder and salt together into a large bowl and set aside.
Heat the milk and 1 stick butter in a small saucepan over medium heat until the butter melts (do not let the mixture boil). Whisk the butter mixture, eggs and creme fraiche in a small bowl, then whisk into the dry ingredients until smooth.
Pour the batter into the prepared pan and bake until a toothpick inserted into the center comes out clean, 12 to 15 minutes. Transfer to a rack to cool slightly before slicing.