Follow the steps in order for the best result.
In a large bowl, whisk together the sour cream and dry ranch dressing mix until thoroughly combined.
If using buttermilk, incorporate it gradually, beginning with 1 tablespoon. Add more, if needed, to achieve a slightly thinned consistency.
Introduce the thawed peas, red onion, celery, cherry tomatoes, and crumbled cooked bacon to the mixture. Toss gently until all ingredients are evenly distributed.
Incorporate the feta cheese, distributing it evenly throughout the salad.
Season generously with salt and freshly ground black pepper, adjusting to your personal taste preferences.
Cover the bowl and refrigerate for a minimum of 2 hours to allow the flavors to meld together harmoniously before serving.