1. Place each chicken breast between 2 sheets of heavy-duty plastic wrap, and flatten to 1/2-inch thickness, using a small skillet or flat side of a meat mallet. Sprinkle chicken with salt and pepper.
2. Melt 1 Tbsp. butter in a large skillet over medium-high heat. Cook 2 chicken breasts in skillet 4 minutes on each side or until done. Transfer to a serving platter; cover with aluminum foil to keep warm. Repeat procedure with remaining butter and chicken.
3. Reduce heat to medium-low; add 3 Tbsp. water and half of tomatoes. Cook 2 minutes, stirring to loosen browned bits from bottom of skillet. Stir in marmalade and vinegar; cook, stirring occasionally, 4 minutes or until tomatoes burst and sauce begins to thicken. Stir in remaining tomatoes, and cook 2 minutes or until thoroughly heated. Stir in basil; add salt and pepper to taste. Spoon sauce over chicken.