Bring a large pot of salted water to a rolling boil. Add dry elbow pasta and cook according to package instructions until al dente, about 8–10 minutes. Once cooked, drain and rinse under cold water.

In a large salad bowl, combine light sour cream, light mayonnaise, Dijon mustard, and lemon juice. Whisk until smooth and season with salt and pepper.

Drain the canned tuna and add it to the bowl with the dressing. Chop gherkins, radishes, cucumber, bell pepper, and onion into small pieces and toss with the dressing.

Fold in the cooled pasta gently until well combined and coated with the dressing.

Serve immediately or divide into airtight containers to store in the refrigerator for up to 3 days.