Wash the tomatoes and arugula. Cut tomatoes into wedges or large dice. Thinly slice the red onion if using. Place arugula in a large serving bowl and set aside.

Prep avocado

Slice avocados just before assembling to prevent browning: halve, remove pit, peel, and slice. Keep slices intact to add to salad just before tossing.

When the potatoes are warm (see Potato cooking), add them to the bowl with arugula. Add tomato wedges and sliced red onion. Sprinkle chopped fresh herbs over the vegetables and crumble the cheese on top, if using.

Add avocado slices on top and toss gently to combine with dressing (see Dressing), taking care not to mash the avocado. Serve immediately.

Potato cooking

Boil potatoes

Place the potatoes in a medium saucepan and cover with 1.5 L cold water. Add 1 tablespoon kosher salt. Bring to a boil over high heat, then reduce to a simmer and cook until potatoes are fork-tender, about 12–18 minutes depending on size.

Drain and cool slightly

Drain potatoes in a colander and let them steam-dry for 1–2 minutes. While still warm, return to the pot or a bowl and toss with 1 teaspoon olive oil to prevent sticking and to add flavor. Taste and season with a pinch of salt and pepper if desired. Allow to cool slightly (5 minutes) before adding to the salad so they don't wilt the arugula.

Dressing

Make dressing

In a small bowl or jar combine 4 tablespoons extra-virgin olive oil, 2 tablespoons fresh lemon juice, 1 teaspoon Dijon mustard, 1 teaspoon honey (or maple syrup), 1 minced garlic clove, 1 teaspoon salt, and 1/2 teaspoon freshly ground black pepper. Whisk vigorously or shake in a jar until emulsified and slightly thickened. Taste and adjust acidity or seasoning as needed.

Just before assembling the salad, pour about two-thirds of the dressing over the warm potatoes and gently toss to coat. Reserve the remaining dressing to drizzle over the finished salad at the table.