In a large pot over medium heat, warm the olive oil. Add the onion, garlic, and ginger. After 2 minutes, add cumin and continue to cook for 2 more minutes. Stir together and cook until onion is translucent (about 5 minutes total).
Add the tomato paste and stir until well distributed in onion mixture. Add the peanut butter and vegetable broth. Stir together then bring to a boil. Add sweet potato. Reduce heat to medium-low, cover and cook for 15-20 minutes or until sweet potatoes are tender, stirring occasionally to prevent sticking.
Add the chopped spinach to the pot, stir, then continue -to cook for another 15 minutes. Using the back of the spoon, mash some of the sweet potato to help thicken the broth. Boil uncovered for 5 minutes. Stir in lime juice and peanuts right before service. Top with roasted peanuts and cilantro. Serve warm over steamed brown rice.