Bring a pot of salted water to a boil and cook the whole-wheat orzo according to the package directions. Drain it well and set it aside while you work on the meatballs. I usually toss it with a tiny drizzle of olive oil so it doesn't clump while it waits.
In a mixing bowl, combine the ground turkey, 1/4 cup of the Greek yogurt, harissa paste, garlic, cumin, smoked paprika, salt, and pepper. Mix gently with your hands or a fork until just combined. Overmixing here will make the meatballs dense, so I try to stop as soon as everything looks evenly distributed.
With slightly damp hands, roll the mixture into about 12 small meatballs. Wetting your hands stops the mixture from sticking and makes shaping much faster. I keep them roughly golf-ball sized so they cook through evenly without drying out.
Heat olive oil in a large skillet over medium heat and add the meatballs in a single layer. Sear for 2 to 3 minutes per side until browned and cooked through, checking that the internal temperature hits 165°F (74°C). I like to resist moving them too early so they get a proper crust.
In the last 1 to 2 minutes of cooking, add the baby spinach and cherry tomatoes right into the skillet with the meatballs. Toss everything gently just until the spinach wilts down. This step is quick, so keep an eye on it or the tomatoes will turn mushy.
In a small bowl, whisk the remaining 1/4 cup of Greek yogurt with the lemon juice and a small splash of water until smooth. Season with a pinch of salt to taste. This drizzle is what ties the smoky meatballs and the earthy orzo together.
Toss the cooked orzo with the sliced red onion and any pan juices left in the skillet, then plate it with the meatballs and vegetables on top. Finish with a generous drizzle of the yogurt-lemon sauce and a sprinkle of fresh parsley. I think this last step is what makes the dish feel finished rather than just thrown together.