1. 1. Cook the pasta: Bring a large pot of salted water to a rolling boil. Add the rotini pasta and cook according to package directions until al dente. This usually takes about 8-10 minutes. Once cooked, drain the pasta thoroughly and rinse with cold water to stop the cooking process and cool it down. Set aside.

2. 2. Prepare the chicken: While the pasta is cooking, pat the chicken breasts dry with paper towels. Cut them into 1-inch cubes. Heat 1 tablespoon of olive oil in a large skillet over medium-high heat. Add the chicken cubes, seasoned with garlic powder, onion powder, salt, and pepper. Cook for 5-7 minutes, stirring occasionally, until the chicken is cooked through and no longer pink in the center. Remove from heat and let cool slightly.

3. 3. Wilt the spinach (optional, but recommended): In the same skillet (or a separate one if you prefer), add the fresh spinach. Cook over medium heat for 1-2 minutes, just until it wilts down. This step helps reduce the volume of spinach and integrates it better into the salad. If you prefer raw spinach, you can skip this step.

4. 4. Whisk the dressing: In a small bowl, combine the fresh lemon juice, 2 tablespoons of extra virgin olive oil, Dijon mustard, and dried oregano. Whisk vigorously until the dressing is well combined and slightly emulsified. Taste and adjust salt and pepper as needed.

5. 5. Assemble the salad: In a large mixing bowl, combine the cooled pasta, cooked chicken, wilted (or raw) spinach, crumbled feta cheese, and chopped red onion.

6. 6. Dress and toss: Pour the prepared lemon-herb dressing over the pasta mixture. Toss everything gently but thoroughly to ensure all ingredients are evenly coated with the dressing.

7. 7. Chill and serve: For the best flavor, cover the bowl and refrigerate the pasta salad for at least 30 minutes to allow the flavors to meld. Serve chilled.