Boil the baby potatoes until tender, about 12 minutes, then drain and let cool.

In a food processor, combine arugula, pine nuts (or walnuts), parmesan cheese, garlic, and lemon juice. Blend while slowly adding olive oil until smooth.

In a large bowl, combine the cooled potatoes, arugula, cherry tomatoes, and red onion.

Toss the mixture with the arugula pesto until evenly coated.