Bring 2 liters of water to a rolling boil in a large pot. Add 1 tablespoon kosher salt. Add 3 cups dried elbow macaroni and cook until just tender (al dente), about 7–9 minutes depending on package instructions.

Reserve 1/4 cup of the hot pasta cooking water, then drain the macaroni in a colander and immediately rinse under cold running water until pasta is cool to the touch. Spread drained pasta on a baking sheet or shallow bowl to cool completely; this prevents the dressing from thinning from residual heat.

While pasta cooks and cools, prepare the vegetables: finely dice 2 stalks celery, 1/2 cup red bell pepper, thinly slice 1/2 cup green onion, grate 1/2 cup carrot and thaw 1/2 cup frozen peas (if using). Combine all vegetables in a large mixing bowl.

Dressing

In a medium bowl, whisk together 1 1/4 cups mayonnaise and 1/2 cup plain Greek yogurt (or sour cream) until smooth.

Whisk in 2 tablespoons apple cider vinegar, 1 tablespoon granulated sugar, 1 teaspoon Dijon mustard, 1 teaspoon celery seed, 1 teaspoon salt, and 1/2 teaspoon freshly ground black pepper until the dressing is homogeneous and slightly glossy. Taste and adjust: add up to 1 tablespoon more vinegar if you like a tangier salad, or a pinch more sugar if you prefer sweeter.

Finish & Garnish

Combine cooled pasta with the bowl of prepared vegetables. Pour the dressing over the pasta and vegetables and toss gently to coat. If the dressing seems too stiff, add up to 1/4 cup reserved pasta water, 1 tablespoon at a time, until you reach a creamy but not soupy consistency.

Fold in 2 chopped hard-boiled eggs, 2 tablespoons chopped fresh parsley and 2 tablespoons sweet pickle relish (if using). Taste and adjust seasoning with additional salt and pepper as needed.

Cover the salad and refrigerate for at least 2 hours, preferably 4 hours or overnight, so flavors meld. Before serving, give the salad a final gentle toss, transfer to a serving bowl, and sprinkle 1/4 teaspoon paprika over the top for color.

Serve chilled. Keeps well covered in the refrigerator for 3–4 days.