Peel, wash, and cut the potatoes into pieces. Place them in a baking dish.
Peel the onion and dice it finely. Heat the olive oil over medium-high heat in a pan and fry the onion until softened, about 3 minutes. Add the tomato paste and cook for 1 minute. Add the water to the pan (this will lift any browned bits from the bottom). Stir in the broth cube until dissolved. Season with salt, pepper, and basil, using plenty of salt so the sauce tastes slightly salty (the potatoes will absorb the salt). Bring to a boil, then pour the sauce over the potatoes.
Wash and pat dry the chicken legs. Season with salt and paprika powder. Place them on top of the potatoes.
Preheat oven to 200°C (392°F). Bake for 45 minutes, until the chicken reaches an internal temperature of 74°C (165°F). Serve immediately.