Heat the oven to 350 degrees. Add 4 tablespoons butter to a 9-by-13-inch pan or other 3-quart casserole dish and transfer to the oven. Tilt the pan to coat the entire pan. Once the butter has melted, about 5 minutes, take the pan out of the oven and let cool.

In a medium pot, melt the remaining 2 tablespoons butter over medium-high. Add the corn, scallions and rosemary, 1 teaspoon salt and several grinds of black pepper, and cook, stirring occasionally, until the corn starts to soften, about 5 minutes. Remove from heat and discard the rosemary sprig.

In a separate bowl, combine the flour, cornmeal, baking powder and 1 teaspoon salt mixing well. Add into the corn mixture. Stir to combine. In a small bowl, whisk together the sour cream and eggs with a fork until combined. Add to the corn mixture along with 1/2 cup grated cheese and stir just until combined, taking care not to overmix.

Pour the batter into the pan, spread evenly, then sprinkle with the remaining 1 cup of cheese. Bake until the cheese is melted and the casserole is set, 30 to 35 minutes. For a golden top, broil for a few minutes. Serve hot.