For the dough, heat milk, 1/2 cup sugar and salt in a saucepan over medium-high heat. Stir until sugar melts and a few small bubbles appear at the edges of the pan. Remove from heat and let cool while you prepare the other elements.
Dissolve yeast and 1 teaspoon sugar in very warm water (90°F to 110°F) in the bowl of a standing mixer (or a large bowl if you don't have a stand mixer). Stir with the paddle attachment (or wooden spoon) until well blended. Let stand 10 minutes.
Beat eggs into yeast mixture. Stir in cooled milk mixture (it should be lukewarm), switch to the dough hook then add in flour a little at a time until dough is elastic. Add melted butter and mix, then add in more flour until dough is elastic and pulls away from the sides of the mixer. Note: you may not have to use all the flour. Do not add so much flour that the dough does not stick to your hands. Set a timer and knead with the dough hook (or knead with hands on a floured surface) for 5 minutes.
Place dough in a buttered bowl and turn it over to coat the entire surface. Cover with plastic wrap and let rise in a warm place 1 hour or until doubled (mine took a little longer than an hour to double).
Punch down dough and turnout onto a lightly floured surface. Knead a few times and cut into two pieces. Roll out each piece to 12x9-inch rectangles.
For the filling, brush the rolled dough pieces with the melted butter. Sprinkle each with half the cinnamon sugar mixture.
Cut the each dough piece into 5 even strip lengthwise. Roll one strip up as if you were making a regular cinnamon roll. When you get to the end, use another strip and continue rolling. When the dough spiral reaches about 6-inches in diameter, (3-4 strips-worth of spiraling) place it in the center of a lightly greased 12-inch cast-iron skillet. Continue spiraling dough strips around the middle. This is a messy job, but just embrace the mess. It'll be well worth the end result.
When all the dough has been used, cover and let rise about 45 minutes or until doubled.
Preheat oven to 400°. Bake for 25-35 minutes, or until golden. Keep a close eye on it so it doesn't over-bake! (Note: Some of you are reporting longer bake times. It's important that this roll gets baked long enough so it isn't doughy in the middle. Allow the top of the roll to become deep golden brown, and then place a sheet of aluminum foil over the roll so it can bake longer without over-browning.)
Whisk together glaze ingredients, adding additional milk as needed. Glaze pastry in the pan while it is still hot. Add additional orange zest if desired. Slice into pieces and serve while still warm.
Source: My Mom's cinnamon roll recipe plus my original glaze recipe