Bring a large pot of salted water to a boil. Add rotini pasta and cook according to package directions until al dente, about 8-10 minutes.
Drain pasta in a colander and rinse immediately with cold water to stop the cooking process. Shake well to remove excess water.
Transfer the cooled pasta to a large mixing bowl. Drizzle with 1 tablespoon of olive oil and toss to prevent sticking.
Add the diced cucumber, halved cherry tomatoes, diced red onion, crumbled feta cheese, chopped dill, and optional kalamata olives to the bowl with the pasta.
In a small bowl, whisk together the remaining 2 tablespoons of olive oil, lemon juice, optional minced garlic, optional oregano, salt, and pepper until well combined.
Pour the dressing over the salad and toss gently to coat all ingredients evenly.
Cover and refrigerate for at least 20 minutes before serving to allow flavors to meld together.
Just before serving, toss again and adjust seasoning if needed.
