Makes 9 rolls. Active time 40 minutes; total time 1 hour 15 minutes
For the filling:
1 1/4 cups light brown sugar
5 tablespoons unsalted butter, cut into chunks, plus more for greasing the pan
2 teaspoons cinnamon
1 large apple ( about 8 ounces), cored, and chopped into 1/4 inch pieces
For the buns:
1/2 cup buttermilk
1 large egg
3 cups all-purpose flour
1 tablespoon granulated sugar
2 1/2 teaspoons baking powder
1 1/2 teaspoons salt
1/2 teaspoon baking soda
12 tablespoons cold unsalted butter cut into small cubes
1. Preheat the oven to 350*F.
2. Grease a 8 by 8 inch baking pan with a bit of butter, set aside. Make the filling: In a small bowl, combine the brown sugar, butter and cinnamon. Using a fork, cut the butter into sugar, working it in until the mixture looks like wet sand. Put in the refrigerator to chill while you prepare the dough.
3. In a small bowl, whisk together the buttermilk and egg; set aside. In a medium bowl, whisk together the flour, sugar, baking powder, salt, and baking soda. Sprinkle the butter over flower mixture and use your fingers to work the butter in. Stop when the mixture looks like sand studded with little chunks. Add the egg mixture and stir with a fork just until the dough begins to hold together. It will look quite ragged and not fully blended, but stop there.
4. Dump out the dough onto parchment paper and knead it just enough to bring it all together, then use a rolling pin and spatula to roll it into a 15″ by 9″ rectangle with straight sides.
5. Sprinkle the dough all over with the filling, leaving a 1-inch border on one of the long sides. Top with the apples and gently press down. Working from the edge opposite the 1-inch border, roll the dough up tightly, like a jelly roll. When you reach the border, give the roll a squeeze and turn the seam upside down.
6. Cut the roll crosswise into 9 equal buns and arrange them in the pan. Bake until golden brown and bubbling, 30 to 35 minutes. Serve warm, right from the pan.
