While the meatballs are cooking, prepare the orzo (or pasta of your choice.)
Melt butter and oil in a 10-inch cast iron frying pan over medium heat. When sizzling, add onion and sauté for 3 minutes, just until softened. Add garlic and lemon zest and sauté for another 2 minutes, until aromatic. Add orzo, stir to coat with oil, and cook for 3 or 4 minutes before adding lemon juice, stock, and wine.
Keep heat at medium and cook for 15 to 20 minutes, until most of the liquid is absorbed and the orzo is soft. The mixture should be creamy but not soupy — cook for a little longer if there’s still too much liquid. Stir in chopped cilantro.
Spoon into bowls, set 4 or 5 meatballs on top, add crumbled feta and serve with tomato sauce on the side.