FOR each serving: Spread 1 Tbsp. bistro sauce onto each of 2 bread slices. Top 1 bread slice with 1 cheese slice and 3 slices each bacon and tomatoes; cover with second cheese slice and remaining bread slice.
SPREAD 2 tsp. butter onto outside of sandwich, spreading 1 tsp. butter on each bread slice. Grill on medium heat 2 to 3 min. on each side or until cheese is melted and sandwich is golden brown on both sides. Cut in half.