Bring a large pot of salted water to a rolling boil, add pasta and cook until al dente, about 8-10 minutes. Drain and rinse under cold water to cool.

Season chicken with garlic powder, salt, and pepper. Grill or sear chicken for 6-7 minutes per side until cooked through. Allow to cool and cut into bite-sized pieces.

In a large mixing bowl, combine basil pesto and red wine vinegar. Add cooled pasta, chopped chicken, halved tomatoes, mozzarella, and spinach. Toss gently to coat.

Taste and adjust seasoning. Add more pesto or salt as desired and drizzle extra red wine vinegar if preferred.

Serve immediately, garnished with basil or extra pesto, or refrigerate in an airtight container for up to 24 hours.