In a medium saucepan, cover potatoes with cold water and bring to a boil. Cook over medium high heat until potatoes are tender, 12 to 16 minutes. Drain well and cool completely.

While potatoes are cooking prepare dressing. In a small bowl, whisk together vinegar, oil, lemon juice, salt and pepper and set aside.

In a large bowl, combine potatoes with green onions, tomatoes and arugula and toss to combine.

Pour dressing over potato salad and toss to evenly coat.

Potato salad can be served room temperature or chilled. Can be made 2 days in advance, keeping arugula and dressing separate and combining just before serving.