Prep the produce. Halve or chop the tomatoes. Dice the cucumber.
Cut the corn off the cob. Slice the peaches. Thinly slice the red onion or scallions.
Dice the avocado last to keep it fresh.
Toast the nuts. In a dry skillet over medium heat, toast almonds, pistachios, or pine nuts for 2–3 minutes, stirring until golden and fragrant. Let cool.
Make the dressing. In a small bowl, whisk lemon zest, lemon juice, grated garlic, Dijon, honey, and a pinch of salt and pepper. Slowly stream in olive oil while whisking until emulsified.
Taste and adjust seasoning. Add red wine vinegar if you want extra brightness.
Combine the base. In a large bowl, add tomatoes, cucumber, corn, peaches, and onion. Season with a big pinch of salt and pepper.
Toss gently.
Add the creamy elements. Fold in avocado and feta (or mozzarella). Drizzle on about two-thirds of the dressing and toss carefully so nothing gets mushy.
Finish with crunch and herbs. Add the toasted nuts, basil, and mint. Toss once more.
Taste and add more dressing, salt, or pepper as needed.
Serve. Transfer to a platter. If using protein, scatter it over the top. Finish with a final squeeze of lemon and a swirl of olive oil.