Place a the pressure cooker over medium-high heat, warm the oil then add the oxtails. Cook on each side for 3-5 minutes.
Stir in the onion, scallions, pimento peppers and garlic. Cook for 2-3 minutes.
Add the water, salt, tomato paste, parsley and thyme. Stir everything.
Lock the lid and let it cook for 45 minutes.
After 45 minutes, turn off the heat and let it the pressure cooker cool completely. It can take at least 10 minutes.
When it is cooled, unlock the lid and place the cooker back on the heat. Add the carrots, pumpkin and/or other veggies. Let it cook for 30 more minutes.
You can add dumplings at 10 minutes before the end of the cooking time.