Pimenton, or smoked paprika, gives these potatoes an unexpected flavor. Any of the several varieties of the spice -- ranging from sweet to hot -- will work well, so take your pick.
Heat 3 tablespoons oil in a large nonstick skillet over medium-high heat. Cook potatoes, covered, for 5 minutes. Season with salt. Add remaining 2 tablespoons oil and the onions; stir. Reduce heat to medium, and cook, covered, for 5 minutes more. Uncover, and cook, tossing often, until potatoes and onions begin to brown, about 8 minutes.
Sprinkle with pimenton, and cook until potatoes and onions are golden brown and tender, about 8 minutes more. Toss with parsley, and season with salt.