In open rice cooker set on High or Sauté setting according to manufacturer’s instructions, melt 4 tbsp butter; cook onion and garlic for 3 to 5 minutes or until slightly softened. Stir in rice, broth, tomatoes, wine, saffron, salt and pepper. (Or, if rice cooker does not have a sauté function or only an on/off switch, cook in skillet on stovetop set over medium heat for 3 to 5 minutes or until slightly softened, then add to rice cooker.)
Turn off High or Sauté setting. Close lid of rice cooker; set on Porridge, Slow or Rice setting; cook for 30 minutes or according to manufacturer’s instructions until tender and creamy. Stir well; set to Warm setting for 10 minutes.
Stir in remaining butter, Parmesan and parsley. Serve immediately.
Depending on rice cooker, the risotto may not need to rest on Warm setting for 10 minutes. Test the texture: if rice is tender and creamy, serve immediately.
If risotto is too thick, stir in up to 1/4 cup hot broth or water for desired consistency.