Buttermilk Biscuits with Green Onions, Black Pepper, and Sea Salt

Position rack in center of oven and preheat to 425 °F. Line baking sheet with parchment paper. Combine buttermilk and green onions in medium bowl. Whisk flour, cornmeal, sugar, and 1/2 teaspoon ground black pepper in large bowl to blend. Add 1/2 cup chilled butter and rub in with fingertips until mixture resembles coarse meal. Add buttermilk mixture and stir until moist clumps form. Gather dough together. Turn dough out onto floured surface and knead gently just to combine, about 3 to 4 turns. Roll out to 3/4-inch thickness. Using floured 2-inch cookie or biscuit cutter, cut out rounds. Reroll scraps and cut out additional rounds. Place 2 inches apart on prepared baking sheet. Brush tops of biscuits with melted butter. Sprinkle each lightly with coarse sea salt and ground black pepper. Bake biscuits until golden and tester inserted into center comes out clean, about 20 minutes. Cool slightly. Serve warm or at room temperature.