Melt the butter with the olive oil in a large skillet over medium-high heat. Cook the onion and garlic in the skillet until they begin to brown; add the apple, carrot, basil, and thyme; reduce heat to medium and continue cooking until the carrots are tender, about 10 minutes. Stir in the vegetable stock, tomatoes, and tomato paste; season with salt and pepper. Raise the heat to high and bring to a boil; cover and cook at least 20 minutes, stirring frequently to keep the soup from burning on the bottom.
Pour the soup into a blender, filling the pitcher no more than halfway full. Hold down the lid of the blender with a folded kitchen towel, and carefully start the blender, using a few quick pulses to get the soup moving before leaving it on to puree. Puree in batches until smooth and pour into a clean pot. Alternately, you can use a stick blender and puree the soup right in the cooking pot.
