Heat 1 tablespoon olive oil in a Dutch oven or large pot over medium-high heat. Add the onion, garlic, and Kosher salt. Cook, stirring occasionally, until the onion is softened, about 5 minutes. Add the tomato paste and cook for another minute, stirring occasionally. Add all but ½ cup of the chopped tomatoes, the beans, broth, 1 cup water, the rosemary sprig, ¼ tsp red pepper flakes, and ½ tsp salt.Bring to a boil. Reduce the heat to medium and simmer for 20 minutes. Discard the rosemary sprig and working in batches, transfer the soup to a blender and puree until smooth. Season with salt. Return to the pot and and cover and keep warm.Top each bowl with the reserved chopped tomatoes and drizzle with olive oil.