Cut a thin slice from top of each tomato. Leaving a 1/2-in.- thick shell, scoop out pulp and discard. Invert tomatoes onto paper towels to drain.
Meanwhile, in a large skillet, melt 4 tablespoons of butter over medium-high heat. Saute the carrot, radishes, green onions, cucumber, peas, parsley, oregano, garlic and salt until the vegetables are tender.
Stuff tomatoes and place in a greased shallow baking dish. In a small skillet, melt remaining butter; stir in the Parmesan cheese, bread crumbs and sugar. Sprinkle over tomatoes. Bake, uncovered, at 400° for 20 minutes or until crumbs are lightly browned.