Heat the oil in a large saucepan over medium-low heat. Add the onions and cook, stirring occasionally, until soft, 10 to 12 minutes.
Add the carrots, broth, 1 teaspoon salt, and 1/3 teaspoon pepper and bring to a boil. Reduce heat and simmer until the carrots are tender, about 10 minutes.
Divide the soup among individual bowls and serve with the crackers, if using.