1. Rinse rice and Lentils in a strainer. 2. Place in a small saucepan and stir in boiling water, cover. 3. Cook for 10 minutes over medium heat. 4. Meanwhile, melt butter or margarine in a saute pan. 5. Add Onion, and saute until golden brown over medium low heat. 6. Stir in Lentil mixture and mint. 7. Season generously with salt and pepper. 8. Slice the tops off tomatoes, and reserve. 9. Scoop out the middles, and reserve. 10. Fill tomato shells with Lentil mixture, and replace the tops. 11. Stand in a baking dish. 12. Chop reserved tomato middles, and place in a small bowl. 13. Mix in oil and garlic.