Heat the olive oil in a large pot over medium heat. Add the onion and garlic and sauté for 3-4 minutes until the onion is translucent.
Add the sweet potatoes and carrots to the pot and stir to combine.
Pour in the vegetable broth and add the thyme and cumin. Season with salt and pepper to taste.
Bring the mixture to a boil, then reduce the heat and let it simmer for 20-25 minutes or until the vegetables are tender.
Remove the pot from the heat and let it cool slightly.
Using a blender, puree the soup until it is smooth and creamy.
While the soup is cooling, heat a large skillet over medium heat. Add the butter and brown sugar and stir until the sugar has dissolved.
Add the sliced apples to the skillet and cook for 3-4 minutes on each side until they are caramelized.
Ladle the soup into bowls and top with the caramelized apples.