Combine beans, water bell pepper & salt, bring to a boil & simmer for 1 1/2 to 2 hours. Add more water as needed.
SOFRITO: Heat oil in a skillet, saute the garlic, onion & bell pepper till tender. Add tomatoes, vinegar, sherry, oregano, cumin, salt & pepper & cook 10 minutes.
When beans are tender, add the sofrito, potatoes & squash. Stir to blend, & cook over a low heat until the potatoes & squash are tender. Either serve as is or puree. Drizzle some olive oil over each serving.
Adapted from Randelman & Schwartz, "Memories of a Cuban Kitchen"