In a large skillet over medium-high heat, warm the oil. Once the oil begins to shimmer, add the cumin seeds and cook until they turn a medium shade of brown, about 1 minute max. Reduce the heat to medium and stir in the fennel seeds. Add the onion and cook until translucent, 4 to 6 minutes.
Stir in the potato, then spread the mixture into an even layer in the pan. Cover and cook for 7 to 10 minutes, until the potato is tender but not mushy (a little charring on the bottom is A-OK.) Stir in the bell peppers and salt. Cover and cook for 3-5 minutes then uncover and cook 2-3 min more, until the peppers are slightly softened. Use a serving spoon or spatula to scrape up the delicious charred bits from the bottom of the pan and stir them into the dish.
Stir in the crushed peanuts and lime juice. Taste and adjust the lime juice and salt, if needed, before serving.