Add chicken; turn to evenly coat both sides of each breast. Gently shake off excess flour mixture.
Melt butter in large skillet on medium-high heat.
Add chicken; cook 10 to 12 min. on each side or until done (165F).
Transfer chicken to platter; cover to keep warm.
Add tomatoes, tomato sauce and garlic to skillet; cook 3 min. or until heated through, stirring frequently. Stir in broth; bring to boil. Simmer on medium-low heat 3 min., stirring frequently.
Whisk in sour cream; cook and stir 2 min. or until heated through. (Do not let sauce come to boil.) Spoon over chicken.