Make the Dough:

Combine the flour, sugar, yeast, and salt in a large zipper-lock bag.

Add the butter, seal and shake to evenly coat the butter. Press the air out of the bag and reseal. Roll over the bag several times with a rolling pin, shaking the bag after each roll, until the butter is pressed into large flakes. About 10 times.

Transfer the mixture to a large mixing bowl and stir in the sour cream, orange juice, water and egg yolk until combined.

Turn the dough onto a floured surface and knead to form a smooth, cohesive ball.

Roll the dough into a 20×12-inch rectangle. Starting with the short side, roll the dough into a tight cylinder. Pat or roll the cylinder flat into a 12×4-inch rectangle and transfer to a parchment paper-lined rimmed baking sheet. Cover with plastic wrap and freeze for 15 minutes.

Filling:

Butter a 12-cup muffin pan with the 3 tablespoons softened butter.

In a medium bowl, stir together the sugars, orange zest, cinnamon, cardamom, and vanilla.

Assemble the buns:

Remove the dough from the freezer and place on a lightly floured surface. Roll the dough into a 20×12-inch rectangle and sprinkle evenly with the filling, leaving a ½-inch border around the edges.

Lightly press the filling into the dough. Starting at the long end, roll the dough into a tight cylinder and pinch to seal the seam.

Trim the ends of the dough from each end and discard.

Cut the cylinder in half, leaving two 10" pieces. Cut each 10" half into 6 1 1/2" pieces totaling 12 equal pieces.

Place each piece cut-side-down into the prepared muffin tin. Cover loosely with plastic wrap and refrigerate for at least 4 hours or up to 24 hours.

Remove the buns from the oven and heat the oven to 425 degrees F. Bake for 5 minutes, then reduce the oven temperature to 325 degrees F.

Bake until the buns are deep golden brown, 40 to 45 additional minutes.

Allow the buns to cool in the muffin tin for 5 minutes, roll in superfine granulated sugar. If you allow them to cool completely in the pan the sugars will caramelize and stick to the pan)

The buns are best served warm.