Start by bringing a large pot of water to a boil. Once rapidly bubbling, add pasta and cook according to package directions until just past al dente.
Strain the cooked pasta and rinse with cold water until it is at least room temperature. Set aside.
Slice a large red onion into halves or quarters. Chop into small diced pieces. If using a ¼ of a red onion, dice the whole thing. If using half, dice it all, but only use half for this recipe. Save the other half for another recipe.
Thinly slice the green part of the scallions or green onions.
In a small bowl, add the greek yogurt, add fresh squeezed lemon juice, red onion, scallions, mustard, salt, and pepper. Whisk until fully combined, taste and adjust as needed.
In a large mixing bowl, add the drained and cooled orzo, the creamy dressing, and the frozen peas. If desired, add any extras (fresh dill or maybe sliced cucumbers) at this step.
Once the pasta salad is fully combined, taste and adjust seasonings as needed. Serve chilled or at room temperature and garnish with drizzled olive oil and flaky salt.