Whisk 2 cups flour with 1 tablespoon baking powder and 1 1/4 teaspoons kosher salt in a large bowl. Pulse 2 cups chopped spring onions and 1 cup sour cream in a food processor until almost pureed. Mix into the flour mixture with a fork to form a shaggy dough. Pat into a round on a floured surface. Cut into eighths. Brush with sour cream. Bake on a baking sheet in a 425 degrees F oven until golden, 18 to 22 minutes.