Pressure Cooker:
Add 1 tablespoon oil and 1/2 green pepper and bring to a boil. Pressure cook on med-low for about 50 minutes.
Warm remaining 1/4 cup oil in a large skillet over medium heat. Add the remainder of the chopped green pepper, your chopped onion, and garlic. Sauté over medium/low heat until the vegetables are soft and translucent.
Once your vegetables are softened and your beans have simmered for 50 minutes, take a slotted spoonful of black beans (not the liquid) from your pot and add to the skillet with the onion mixture.
Using a wooden spoon or a meat mallet, smash your ladle of black beans into the onion mixture and stir to combine. (they don't have to be completely smashed but just enough to pop them open and incorporate them into the onion mixture)
Add all of the skillet contents and 2 cups of water back into the large pot of black beans and stir.
Add 3 cups of water, if necessary and remainder of ingredients (oregano, salt, black pepper, sugar, cumin, vinegar) into the pot and stir.
Cover and simmer for another 20 minutes.