How to Make It
In a large saucepan, melt 1 tablespoon of the butter in 1 tablespoon of the olive oil. Add the sliced onion and smashed garlic and cook over moderate heat, stirring occasionally, until softened, about 5 minutes. Add the tomatoes and their juice, the water, heavy cream, sugar, crushed red pepper, celery seed and oregano and season with salt and pepper. Bring the soup to a boil over high heat, breaking up the tomatoes with the back of a spoon. Reduce the heat to moderate and simmer for 10 minutes.
Meanwhile, in a small skillet, cook the remaining 1 tablespoon of butter over moderately high heat until it begins to brown, about 1 minute. Scrape the browned butter into a medium bowl. Add the olive oil to the skillet. Add the diced bread and cook over moderately high heat, stirring occasionally, until it is slightly browned, about 6 minutes. Transfer the bread to the browned butter and toss well.
Working in batches, transfer the tomato soup to a blender and puree until smooth. Return the soup to a clean pot and rewarm the soup if necessary. Season the soup with salt and pepper. Ladle the soup into bowls and serve with the croutons.