Preheat oven to 375 degrees. Line a baking sheet with foil.
In a medium bowl, combine potatoes, 2 tablespoons olive oil, 2 Tablespoons dry rub mix. Season with salt and pepper.
Pour onto your prepared sheet pan and bake until potatoes are fork tender, about 20 minutes.
Meanwhile, in a small bowl, place remaining 2 Tablespoons olive oil, 1 Tablespoon dry rub mix, and vinegar.
Whisk to combine, and season with salt and pepper. You might want to use a little water to thin the mixture to your desired consistency.
Once potatoes are cooked, place arugula, red onions, tomatoes and potatoes in a serving dish. Toss gently to combine, then drizzle over the dressing.