My preferred pasta for this dish is orecchiette. I've also used whole wheat elbow macaroni. Today I substituted thinly sliced red cabbage for the carrots in the recipe. The biggest change was, I didn't heat the yogurt.
Yogurt tends to separate when heated, especially the non-fat variety. This doesn't seem to affect the taste, but it has a rather unappetizing appearance. I also notice that the color photo of Pasta with Smoked Salmon looks as though the yogurt hadn't been heated. Time to experiment!
Today I got the tuna (one 4-oz can, well drained) and vegetables ready. Then I cooked the pasta, drained it, and tossed it with one teaspoon of olive oil, some parsley flakes, and some garlic powder and salt. Next, I added the tuna, flaking it with a fork as I removed it from the can. Then I tossed in the veggies. Last, I folded in the yogurt. I didn't add any water to the yogurt.
This works as well as heating the yogurt and water, as the recipe specifies. It turns out cold, of course, but it still tastes good. And that's what matters -- right?