2-3 medium sized boiled Yukon gold potatoes (skin on) cut into one inch cubes
2 cups of sweet grape tomatoes, cut in half
1/2 cup thinly sliced sweet onion (use a lot less if it's not a sweet onion)
1 handful (about a cup) of arugula (a.k.a. rocket) leaves, chopped
1 tablespoon olive oil
1 tablespoon mayonnaise
1 teaspoon mustard
1/2 teaspoon garlic salt
1 oz. feta cheese or other sharp cheese (optional). If you don't use feta, add a little extra salt.
If the potatoes are still warm, go ahead and toss in the olive oil and garlic salt on them first, and then let them cool completely before adding the other ingredients. Now because you are using tomatoes, this isn't really a potato salad that you mix up ahead of time, but you can do all the chopping ahead and then mix it all together at the last minute. The arugula adds a peppery-ness to it, so you don't need to add pepper. If you do I would go with white pepper, not black. If you aren't doing dairy, a good substitute to add richness is a crumbled hard boiled egg yolk (no white, that's not a great texture here.)
I just ate this for lunch and it didn't need bread or anything. But it would go great with fried chicken too!