Preheat your oven to 375F. After the dough has finished the next rise, turn out the dough on a well-floured surface. Dust your rolling pin with flour and roll out the dough to some 1/2 inch thick rectangle.
Then put in the Muir Glen tomato sauce into the buns and spread out the dough over. Be certain that you leave a 2-inch border round the dough without even filling.
After that, add the caramelized onion & spinach mixture on top of the tomato sauce and spread out evenly. Sprinkle the fresh basil on top.
Now that all of the toppings are around the dough, then roll it into a log. Be certain you tuck at the filling as you move so it doesn't escape the sides of the dough. Pinch the dough together in the seam to seal the rolls. After that, roll the dough over so the pinched seam is facing down.
Cut the dough into 12 evenly sized pieces and put into a greased 9x13" pan. As a last measure, sprinkle the nutrient yeast on top of the buns.
Bake for 34-38 minutes till the buns are browned on the outside and cooked, however tender, on the inside.
Slice the buns and serve with a side of hot tomato sauce for dipping.