Directions

1. Whisk the water and yeast in a large bowl and let sit for 5 minutes to dissolve; the mixture will bubble slightly. Add the cake mix and flour and stir vigorously for 1 minute until the dough comes together and no dry flour remains; don't be tempted to overwork or knead the dough or it will get very sticky and hard to work with. Cover with plastic wrap and let the dough rise in a warm, draft-free area until doubled in volume, 1 hour to 1 hour 20 minutes.
2. Meanwhile, whisk together the brown sugar, cinnamon and 1/4 teaspoon salt in a medium bowl until no lumps of sugar remain. Work in 12 tablespoons of the butter and stir until completely combined. Set aside until ready to assemble.
3. Beat the cream cheese, confectioners' sugar, cream, vanilla, the remaining 4 tablespoons butter and 1/4 teaspoon salt in a medium bowl until light and creamy, about 2 minutes. Set aside until ready to serve.
4. Gently deflate the dough by lifting it up around the edges and letting it fall back into the bowl, turning the bowl and repeating if needed. Transfer to a clean work surface lightly dusted with flour. Roll into a 12-by-16-inch rectangle, pushing the edges towards the center to make the sides straight. Spread the butter-brown sugar mixture over the dough in an even layer, leaving a 1/4-inch border around the edges. Starting on one of the shorter sides, tightly roll into a log, pressing the sides occasionally to keep them flush.
5. Grease a 13-by-9-inch baking pan with butter. Cut the dough log crosswise into 12 equal pieces and arrange them cut-side up in the pan, gently shaping the rolls to make them fit in the pan. Let rise, covered, in a warm, draft-free area until almost completely covering the pan, about 30 minutes.
6. Arrange an oven rack in the center of the oven and preheat to 350 degrees F.
7. Bake until the rolls are puffed and brick red and the filling is bubbling, 20 to 25 minutes. Let cool until set, about 30 minutes.
8. Spread the frosting over the warm rolls and serve.