In a large (eight- to 10-quart) soup pot, heat olive oil over medium-high heat. Add onion, pepper, celery, sweet potato, apples, and sausage. Sauté, stirring occasionally, until onion is translucent, five to 10 minutes.

Reduce heat to medium-low. Add kale and garlic; cover. Cook for two minutes.

Add broth, diced tomatoes with their liquid, salt, and pepper. Cover; cook for 15–20 minutes, until vegetables are tender.

If using, add a dash of sriracha to the bowl just before serving.