2 cans (28 ounces each) whole peeled tomatoes in juice (with basil if available)
In a 5-quart saucepan or Dutch oven, melt butter over medium heat; add oil and onion, and season with salt and pepper. Cook until onion is translucent, about 5 minutes. Stir in flour and tomato paste; cook 1 minute.
To saucepan, add thyme, broth, and tomatoes, breaking up tomatoes with your fingers. Bring to a boil; reduce heat and simmer, 30 minutes. (Remove thyme sprigs before blending.)
Using an immersion blender, puree soup in pot, leaving a fair amount of the tomatoes in chunks. Or, working in several batches, puree half (5 cups) of the soup in a conventional blender until smooth; return to pot. Season with salt and pepper. Serve immediately.