Toss lettuce, radishes and onions in a large salad bowl; set aside. In a skillet, cook bacon until crisp. Remove to paper towels to drain. To the hot drippings, add vinegar, lemon juice, sugar and pepper; stir well. Immediately pour dressing over salad; toss gently. Crumble the bacon and sprinkle on top. Yield: 6-8 servings.