In the bowl of a stand mixer fitted with the dough hook, whisk together 3 2/3 cups all-purpose flour and 2 1/4 teaspoons rapid-rise dry yeast (one package). - If using active dry yeast instead, dissolve the yeast in the warmed milk (see step 2) and let sit 5–10 minutes until foamy before continuing.

Warm 1/2 cup whole milk to approximately 100°F. Melt 6 tablespoons unsalted butter and let it cool to approximately 100°F.

With the mixer running on medium speed, add the warmed milk and the cooled melted butter to the flour/yeast mixture. Add 1/2 cup sour cream, 1/3 cup sugar, 2 teaspoons kosher salt, and 1 lightly beaten large egg.

Mix on medium speed about 5 minutes, until the dough is smooth and elastic and pulls away from the sides of the bowl but still sticks slightly to the bottom.

Spray a large bowl with nonstick cooking spray. Transfer the dough to the prepared bowl and turn once to coat the top with oil. Cover the bowl and let the dough rise in a warm, draft-free place until about doubled in size, about 1 to 2 hours.

Spray a 9-inch round pan (about 2 inches deep) with nonstick cooking spray and set it aside.

After the dough has doubled, lightly punch it down. On a lightly floured surface, roll the dough into a 14" x 10" rectangle.

Spread 6 tablespoons softened unsalted butter evenly over the rolled dough.

In a small bowl, stir together 2/3 cup sugar and 2 tablespoons orange zest. Sprinkle this sugar–zest mixture evenly over the buttered dough.

Starting at one long side, roll the dough tightly into a log. Pinch the seam to seal.

Slice the log into 9 to 10 even rolls. Place the rolls, cut side down, into the prepared pan, spacing them evenly.

Cover the pan and let the rolls rise in a warm, draft-free place until almost doubled in size, about 45 minutes to 1 hour. Preheat the oven to 350°F during the last 10–15 minutes of the rise.

Bake the rolls at 350°F, uncovered, until golden brown, approximately 30 minutes. Remove from the oven.

Let the rolls cool in the pan on a wire rack for 10 to 15 minutes.

In a medium bowl, stir together the remaining 1 tablespoon orange zest, 2 cups confectioners' (powdered) sugar, and 4 tablespoons fresh orange juice until smooth.

Drizzle and spread the icing over the warm rolls. Serve.