Add the onion, garlic, potatoes and ground beef to a preheated skillet set over medium-high heat. Season with the garlic, onion, cumin, chile powder, oregano, salt and pepper. Use a wooden spoon to break up the meat and incorporate all the seasonings. Stir occasionally.
Once the meat has started to caramelize and the veggies are lightly browned and softened, add the water. Place a lid on the skillet and reduce heat to medium-low. Let simmer until all the liquid has gone and the potatoes are fork tender. If the potatoes are not tender yet, add an additional ¼ c. of water and repeat the process.
Toss in the peas and olives, if using. Stir.
Taste for seasoning and add as necessary or desired.
Replace the lid but turn the heat off. Let sit on the cooling burner for 5 min. Stir occasionally to prevent sticking.