In a small bowl, mix Dei Fratelli Chili Ready Diced Tomatoes, ½ cup bbq sauce, ¼ cup butter, and garlic until well combined.
Line a 9x13 baking dish with aluminum foil. Place chicken in a single layer in the dish and stuff the tomato mixture under the skin of each breast. Use remaining mixture and remaining bbq sauce to drizzle on top.
Cover tightly with another layer of foil. Place chicken on a rack in the upper third of the oven and bake for 30 minutes.
Remove top layer of foil and bake for an additional 25 minutes, or until chicken is fully cooked.
While the chicken cooks, place the potatoes in a microwave-safe dish and fill halfway with water. Microwave for 10-12 minutes, or until potatoes are tender. Drain and place in a medium bowl.
To the potatoes, add Dei Fratelli Seasoned Diced Tomatoes and ½ cup butter. Mash together using a potato masher or large fork.
Place potato mixture in a 9x13 pan in an even layer. Sprinkle cheddar cheese on top so all potatoes are covered. Cover with a piece of foil and bake on center rack for 30 minutes.
Remove foil and cook for an additional 15 minutes.