Savory Corn and Pepper Muffins

INGREDIENTS

• 1 cup all-purpose flour
• 1 cup yellow cornmeal
• 3 tablespoons sugar
• 1 tablespoon baking powder
• ½ teaspoon baking soda
• 1 teaspoon salt
• 1½ teaspoons chili powder
• ¼ teaspoon freshly ground black pepper
• 1 stick (8 tablespoons) unsalted butter, melted and cooled
• 1 cup buttermilk, at room temperature
• 1 large egg yolk
• ¼ cup corn kernels, fresh or frozen
• 1 small jalapeño pepper, seeded and finely diced
• ¼ red bell pepper, seeded and finely diced