Heat the butter and olive oil in a large saucepan and sauté the onion and garlic until the onion is translucent, approx. 5 minutes. Add the tomatoes, water, cream, salt, red pepper flakes,oregano, basil and sugar. Bring to a boil, then lower the heat to a simmer and simmer for 15 minutes.
Remove from the heat and puree in batches in the container of a blender. Return the soup to the pot and reheat to a simmer, seasoning to taste with more salt and pepper.
Meanwhile, to make the brown butter croutons, preheat the oven to 350°F. Heat the butter in a small pan over medium heat and cook, stirring often, until the butter is golden brown and aromatic, about 3 minutes after the butter melts. Remove from the heat. Put the bread cubes in a bowl and pour the brown butter over them, tossing to coat. Season to taste with salt, pepper, and garlic and toss again. Spread the bread cubes on a baking sheet and place it in the oven. Bake until the croutons are toasted and golden, about 20 minutes, stirring occasionally. Remove the pan from the oven.