1. In a medium saucepan, bring 4 1/4 cups of water and salt to a boil. Whisking constantly, slowly add the grits in a steady stream. Reduce heat to low.
2. Cook, stirring frequently, until the grits are thick, creamy, and pulling away from the side of the pan, 15-20 minutes.
3. Add the Cheddar and stir until it melts.
4. Add the scallions, pepper, and butter and stir.