Preheat your Blackstone griddle to low heat and lightly coat the surface with olive oil.
Add the diced onion, zucchini, yellow squash, asparagus, and cherry tomatoes to the griddle. Season with Tuscan Herb Seasoning and cook for 5–7 minutes, stirring occasionally, until the vegetables are tender-crisp.
Push the vegetables to one side of the griddle. Add the tortellini and a small splash of water, then cover with a basting dome. Steam for 2–3 minutes, or until the tortellini is heated through.
In a bowl, whisk together the olive oil, red wine vinegar, lemon zest, lemon juice, salt, pepper, Parmesan cheese, and chives to make the dressing.
Add the steamed tortellini to the vegetables and toss gently to combine. Pour the dressing over the mixture and stir until everything is evenly coated.
Fold in the chopped basil and cook for 1 additional minute.
Garnish with extra fresh basil and grated Parmesan cheese, if desired. Serve immediately and enjoy.