Slice tomatoes in half, scoop out seeds, and place in a baking dish sliced-side up. Sprinkle with and salt and pepper . Bake for 5 minutes. Remove tomatoes from oven, drizzle with olive oil, and bake an additional 10 minutes.
While baking tomatoes, mix together cucumber, yogurt, olives, basil, and sugar. Stir in feta cheese. Season to taste with salt and pepper.
Remove tomatoes from oven, fill with cucumber mixture, and sprinkle with parsley. Serve immediately.