In the bowl of a stand mixer fitted with a paddle attachment, place the flour, xanthan gum, tapioca starch/flour, granulated sugar, yeast, and cream of tartar. Whisk to combine well.

Add the cream of tartar, salt, cinnamon, cardamom, allspice, lemon zest and orange zest, and whisk again to combine well.

Add the vanilla, vinegar, milk, 1 egg and egg yolk, and the melted butter. Beat until very smooth and uniform in color and texture. The dough will be very thick.

Turn off the mixer, add the currants to the dough, and mix until they’re evenly distributed throughout the dough.

Cover the dough and allow it to rest, covered, for about 45 minutes. It won’t visibly rise very much.

Line a rimmed baking sheet with unbleached parchment paper, and set it aside.

Divide the dough into 8 approximately equal pieces. Working with one piece at a time on a surface lightly dusted with tapioca starch, roll each piece of dough into a tight ball.

Place the buns about 1½ -inches apart on the prepared baking sheet.

Cover the baking sheet with lightly oiled plastic wrap, and place in a warm, draft-free environment to rise until about 150% of their original size.

While the buns are nearly done rising, preheat your oven to 350°F and make the egg glaze. In a small bowl, place the egg and beat it well. Add the ¼ cup of confectioner’s sugar, and beat to combine well.

Once the rolls have finished rising, with a sharp knife, slice a cross (+) on top of each roll about ¼-inch deep. Using a pastry brush, brush the top of each bun generously with the egg glaze.

Place the baking sheet in the center of the preheated oven and bake until the buns are golden brown and firm to the touch, about 30 minutes.

Allow the buns to cool for about 10 minutes on the baking sheet before transferring them to a wire rack to cool completely.

Once the buns are cool, make the icing for the cross. In a medium-sized bowl, combine the ½ cup confectioner’s sugar with 1 teaspoon milk. Mix to combine well.

Once the rolls have cooled completely, place the icing in a pastry bag fitted with a small, plain tip, and pipe a cross (+) neatly over the cross you made with a knife, on each roll.

Allow the icing to set and serve. Leftovers can be frozen in a single layer, then wrapped tightly with freezer-safe wrap.