Polenta thickens as it cools, so fill the peppers as soon as it's cooked. If serving immediately, bake peppers right after they're filled (reduce cooking time slightly).
- 4 tablespoons butter
- 1 onion, finely chopped
- 1 1/2 teaspoons finely chopped fresh rosemary (or 3/4 teaspoon dried rosemary, crumbled)
- Coarse salt and ground pepper
- 1/2 cup yellow cornmeal
- 1 package (10 ounces) frozen corn kernels, thawed
- 1 cup shredded sharp white cheddar cheese
- 4 red bell peppers, halved lengthwise through stem, ribs and seeds removed
In a medium saucepan, melt 1 tablespoon butter over medium-high. Cook onion, stirring often, until lightly browned, 5 minutes. Add 3 cups water, rosemary, 2 teaspoons salt, and 1/4 teaspoon pepper; bring to a boil.
Whisking constantly, gradually add cornmeal, whisking until incorporated before adding more. Reduce to a simmer; cook, whisking frequently, until thickened, about 5 minutes. Remove from heat; stir in corn, remaining 3 tablespoons butter, and half the cheese until melted.
Place peppers in a large baking dish; fill with polenta mixture. Cool to room temperature. Cover tightly with foil; refrigerate until ready to use, up to 2 days.
Preheat oven to 400 degrees. Pour 1/2 cup water in bottom of baking dish. Cover with foil; bake 30 minutes. Remove foil; sprinkle with remaining cheese.
Return to oven; bake, uncovered, until cheese is golden and peppers are very tender, about 30 minutes more. Serve immediately.