Preheat an oven, then drizzle of olive oil in a large baking dish. Slice the top of each tomato, but reserve the tops. Use a spoon to scoop out the pulp and any seeds, then discard. Place the tomatoes cut side up in the baking dish, then sprinkle the insides with Kosher salt, reserving the rest.
Heat olive oil in a skillet over medium-high heat. When hot, add diced onion and cook, stirring occasionally. Add minced garlic, cook 1 minute more, then add ground lamb. Season with remaining 1 tsp Kosher salt, ground cinnamon, and black pepper, then cook until browned on all sides.
Stir in cooked rice, red wine vinegar, and feta cheese, chopped cilantro, and chopped parsley, then mix well. Taste and adjust seasoning as needed.
Place heaping spoonfuls of the filling inside each tomato so that it’s mounted on top. Bake then serve hot or room temperature with additional chopped parsley, feta cheese, and a sprinkle of flaky sea salt.