Preheat the oven to 375 degrees F (190 degrees C). Grease a 9x13-inch casserole dish.

Sauté butter and onion in a medium saucepan over medium heat until onion is translucent, 3 to 4 minutes. Add salt, pepper, basil, brown sugar, and tomatoes; mix well. Stir in bread until well combined. Pour tomato-bread mixture into the prepared dish.

Bake in the preheated oven for 30 to 35 minutes. Enjoy.