I make this recipe from home-canned tomatoes or roasted whole tomatoes. You can substitute a 28-ounce can whole peeled or, preferably, roasted tomatoes. Serve with cheese toasts or grilled cheese for dipping for a simple weeknight supper.
Combine the onion, tomatoes, thyme and paprika in a saucepan and bring to a boil over medium heat. Reduce the heat to simmer until the onions are softened, about 20 minutes. Season to taste with salt and pepper.
Use an immersion blender to puree the soup. Or, for a very smooth soup for swirling, transfer the soup into a blender. (Warning: hot soup tends to shoot out of the blender.) Put on the lid and cover it with a kitchen towel to avoid splattering. Pulse the soup 2-3 times with very short bursts, then puree until very smooth.
Pour into soup bowls and serve with a drizzle of the sour cream, if using.