Drain the tomatoes in a sieve to remove excess liquid while you prepare the rest of the ingredients.

In a bowl, combine the tomatoes, onion, garlic, olive oil, lemon juice, basil, tarragon, salt, and pepper. Add the croutons and toss well.

Divide among 4 plates. Top each serving with an equal amount of the arugula. With a vegetable peeler, shave the Parmesan over the salad. Serve immediately.