Heat a large skillet over medium heat and add the oil. When hot, add the potatoes and cook, stirring occasionally, for 2 minutes. Add the garlic, bell pepper and onion and continue to cook, stirring occasionally, until the vegetables are tender, 3 to 5 minutes. Remove from the heat, add the vinegar and parsley if using and transfer to a serving platter.
Wipe out the skillet, then heat over high heat and add some oil. Season the steak with the spice rub. When hot, add the steak and cook to desired doneness, about 2 minutes per side. Season with salt and pepper to taste.
Top the vegetables with the steak.
For more ingredient substitution ideas, see the article below.