Add vegetable oil to a 4-5 quart pot and add the onion and garlic. Cook to soften; about 3 to 5 minutes on medium heat.
Add the ground beef to the onions and garlic and continue cooking, stiring occasionally until the meat is just done, about 10 to 15 minutes. Drain off the fat and return to the pot.
Meanwhile, dice the potatoes, peeled or not. When meat mixture is browned and drained, add the potatoes and the cumin. If using the cumin seeds, rub between the palms of your hands to release the oils a bit. If you prefer the ground cumin, just add. Cook and stir for about 5 minutes.
Add the water and the tomato paste and stir til the paste is completely disolved. Add the salt and pepper and turn up to bring to a boil. Continue cooking, uncovered, at about medium high heat until potatoes are tender; about 25 to 30 minutes