Heat 2 tablespoons of the olive oil in a small Dutch oven or large saucepan, add the onions, and cook over low heat for 10 minutes, or until translucent but not brown.
Stir in the rice and 2 teaspoons of salt and cook over low heat for 5 minutes.
Add the hot stock and the saffron and cook, covered, over the lowest heat for 20 minutes, or until the rice is tender.
Optional, transfer the rice to a baking dish, add the stock and bake at 350 F for 50-60 minutes, or until liquid is absorbed and the rice is tender.
Meanwhile, in a medium sauté pan, heat the remaining 2 tablespoons of olive oil, add the garlic, and cook over low heat for 50 seconds. Add the drained diced tomatoes and cook for 5 minutes, stirring from time to time. When the rice is done, add the tomato mixture, 3/4 teaspoon salt, the pepper, parsley, and Parmesan, Stir with a fork, season to taste, and serve hot.