In a small bowl, whisk together the flour and water until no lumps remain. Microwave in 25 second increments, stirring between each increment, until mixture has become a smooth paste (should be about 50 seconds). 

In the bowl of a stand mixer, combine flour paste and milk then whisk until smooth. Add egg and egg yolk and mix until combined. Add flour and yeast, then place bowl in the stand mixer fitted with dough attachment. Let mix for one or two minutes or until all the flour has been moistened. It helps to scrape down the bowl during this process to help the flour incorporate. Let the mixture stand for 15 minutes. 

Add salt, sugar, and zest then mix on medium-low speed for about five minutes, scraping down the sides of the bowl to encourage the dough to stick together. Add the butter to the dough, then mix for an additional five minutes, scraping down the bowl as necessary. The dough will stick to the bottom of the bowl. 

Turn out the dough onto a lightly floured surface and knead for less than 30 seconds to make a smooth, round ball. Transfer the dough, seam side down, into a lightly greased bowl. Lightly spray the dough with non-stick spray, then cover the bowl tightly with plastic wrap. Let rise until doubled, 40 minutes to one hour. 

In a small bowl, mix together granulated sugar, brown sugar, and orange zest until well incorporated. Set aside.

Line a 9x13 cake pan with a foil sling and lightly grease with cooking spray. Set aside.

After the dough has proofed, turn it out onto a lightly-floured surface and roll into an 18x15 rectangle, with the long edge nearest you. Spread the softened butter evenly over the surface of the rectangle, making sure to leave a 1"  border on the top. Spread filling evenly over the surface of the dough. Starting with the long side of the dough, roll the dough into a cylinder, making sure not to roll the dough too tightly. Pinch the seam to seal, then make any adjustments needed to the roll so it is 18" long and even. Cut the log into 12 slices with dental floss and arrange evenly in the pan. Cover the pan with plastic wrap and let proof for 40 minutes to an hour, or until the rolls are puffy and touching each other. 

Toward the end of the second proof, preheat oven to 375 F and adjust rack to lower-middle position. Bake rolls until golden brown and internal temp measures 200 F (about 25 minutes). Remove and let cool for about 15 minutes. 

While the buns are cooling, cream together cream cheese, powdered sugar and zest. Add juice, vanilla, and salt, and mix until smooth and free from lumps. Spread or drizzle over the rolls. Enjoy!