Heat olive oil in a large saute pan. Add onions and mushrooms and cook over medium heat until cooked down, about 5-7 minutes
Stir in rice then add wine and cook until it all evaporates.
Turn heat down to medium low then add 1/2 cup broth and stir frequently until almost evaporated. Then add another 1/2 cup. Repeat process until all the broth is evaporated and rice is tender about 26-28 minutes.
Mix in tomato sauce, spinach, garlic powder, and black pepper.
Remove from heat and stir until spinach is wilted then add cheese.
Garnish with additional cheese if desired.