Cook the rigatoni pasta according to package instructions until al dente. Drain and rinse under cold water to cool.
In a large bowl, combine the cooked rigatoni, chopped spinach, cherry tomatoes, feta cheese, dried cranberries, and red onion.
In a separate small bowl, whisk together the olive oil, lemon juice, Dijon mustard, garlic powder, salt, and pepper until well combined.
Pour the dressing over the pasta salad and toss gently to combine all ingredients evenly.
Chill the salad in the refrigerator for at least 30 minutes before serving to allow the flavors to meld.