Place beans in a medium saucepan and cover by about 2 inches of water. Bring to a boil; remove from heat and let stand for 1 hour. Drain and rinse.
In a stockpot over medium-high heat, warm olive oil. Add onion, garlic, serrano chile, and 1/4 tsp. kosher salt. Saute until onion is translucent, about 5 minutes. Stir in hot or sweet paprika and tomato paste; cook for 1 minute. Add beans, chicken stock or water, and cilantro. Bring to a boil. Reduce heat to low and simmer, partially covered, for about 35 minutes.
Peel, seed, and cut half small sugar pumpkin. Add pumpkin to bean mixture, plus additional stock or water to cover, and simmer, partially covered, until tender, about 25 minutes more. Remove and discard cilantro. Serve immediately.