Cook the pasta. Bring a large pot of salted water to a rolling boil. Cook the pasta until al dente according to package directions. Drain and rinse under cool water to stop the cooking and remove excess starch. Shake off well.

Make the dressing. In a large bowl, whisk together olive oil, balsamic vinegar, lemon juice, Dijon, garlic, oregano, salt, pepper, and red pepper flakes. Taste and adjust seasoning. The dressing should be tangy and well-salted.

Toss the warm pasta. Add the cooled pasta to the bowl with the dressing and toss to coat. Let it sit for 5 minutes so the pasta absorbs some flavor.

Add the proteins and veggies. Add the chicken, tomatoes, mozzarella, and spinach (if using). Gently toss so the mozzarella doesn’t break apart. Fold in the red onion and nuts if you like.

Finish with basil. Add torn basil right before serving. Toss lightly and taste again. Add a splash more balsamic, a drizzle of olive oil, or a pinch of salt if needed.

Serve your way. Enjoy immediately at room temperature, or chill for 30–60 minutes to let the flavors meld. It’s excellent either way.