Cut each potato into an even rectangular shape by cutting off the bottom, top, and sides, then cut into 1/2-inch cubes. Place potatoes in a medium, heavy saucepan. Add enough cold water to cover, season with salt, and bring to a boil. Reduce heat and simmer until potatoes are slightly tender, about 10 minutes. Remove from the heat and drain potatoes on paper towels.
In a large saute skillet, heat olive oil over medium heat. Add the onions and saute until soft, about 3 minutes. Add the garlic and saute for 30 seconds. Add the drained potatoes and cook, turning, until browned on both sides.