Preheat oven to 450°. Place tomatoes in a 15x10x1-in. baking pan, cut side down; brush tops with 1 tablespoon oil. Roast 20-25 minutes or until skins are blistered and charred. Remove and discard skins.
In a 6-qt. stockpot, heat remaining oil over medium-high heat. Add onions; cook and stir until tender. Add garlic; cook 1 minute longer. Stir in broth, orange juice, tomato paste and roasted tomatoes; bring to a boil. Reduce heat; simmer, uncovered, 45 minutes.
Stir in orange zest, butter, cilantro, honey and salt. Remove from heat; cool slightly. Process soup in batches in a blender until smooth. Return to pot; heat through.