In a large mixing bowl, combine the ground chicken, panko breadcrumbs, egg, fresh parsley, ground cumin, ground cinnamon, smoked paprika, and kosher salt. Mix gently until just combined.
Divide the chicken mixture and roll into 1 1/2-inch meatballs using damp hands.
Heat the olive oil in a large skillet over medium-high heat. Add the meatballs in a single layer, ensuring not to overcrowd the pan.
Pan-fry the meatballs for 8 to 10 minutes, turning occasionally, until they are golden brown on all sides and cooked through to an internal temperature of 165 F.
In a small bowl, whisk together the Greek yogurt and grated cucumber to create a quick tzatziki sauce.
Serve the warm Moroccan chicken meatballs topped with the tzatziki sauce, alongside the thinly sliced red onion.