Coat a large saucepan with cooking spray and set over medium heat. Add onion and bell pepper; cook, stirring often, until softened, about 3 minutes.
Stir in the sweet potato, carrots and garlic; cook for 1 minute, stirring often. Add the ginger, cloves, salt and cayenne; cook for 30 seconds.
Pour in the vegetable broth and bring to a simmer, scraping up any browned bits from the bottom of the pan. Stir in the peanut butter until smooth.
Cover, reduce the heat to low, and simmer slowly, stirring once in a while, until the sweet potatoes are tender, about 30 minutes.
Add the spinach; cook, stirring occasionally, for 10 minutes. Yields about 1 ⅔ cups per serving.