Heat the vegetable oil in a medium saucepan over medium-high heat.
Add the garlic, onion, bell pepper, culantro, cilantro stems, chicken bouillon, annatto, tomato sauce, olives, oregano, and black pepper. Cook, stirring occasionally, for about 5 minutes, until the onion begins to soften and the mixture becomes fragrant.
Add the beans with their liquid and the water. Stir to combine and bring to a gentle boil.
Once boiling, add the cubed squash and stir.
Reduce the heat to medium and let simmer for about 15 minutes, or until the liquid reduces slightly and thickens. The beans should have a light, saucy consistency.
Remove and discard the garlic, onion, bell pepper, culantro, and cilantro stems.
Stir in the fresh lime juice. Taste and adjust salt if needed.
Serve warm as a side dish with white rice and your favorite Dominican meat dishes.