Place butter in a 9x13 baking dish. Bake 5 minutes or until melted. Remove from oven.
Add rice, tomatoes, broth, onion, and salt. Stir to combine. Cover with foil and carefully place back in oven.
Bake for 30-35 minutes. While rice is baking, warm chicken and prepare mozzarella and basil.
Remove rice from oven and fluff with a fork. Add warmed chicken, mozzarella, and basil. Toss to combine. Serve immediately.
Arborio rice is the only kind I've tried for this recipe. Jasmine rice might work if you can't find it. Do not use instant rice.
For the chicken, you can use rotisserie chicken or pre-cook chicken breasts. To cook chicken breasts, I prefer using a slow cooker. Season with salt, pepper, onion powder, and garlic powder plus a cup of water. Cook on low for 7 hours or high for 4 hours.
For the mozzarella, I prefer to use the fresh kind that is usually found near the deli.
If you like your tomatoes fresher, just toss in at the end with the chicken.