Put carrots into a small bowl, and cover with cold water; let stand 10 minutes. Drain well. Set aside.
Whisk together lemon juice, vinegar, 1 teaspoon salt, and 1/4 teaspoon pepper in a small bowl. Gradually whisk in oil until emulsified; set aside. Toss lettuces, arugula, and endive in a large bowl; cover with a damp towel, and refrigerate until ready to use.
Prepare an ice-water bath; set aside. Bring a large pot of water to a boil. Add 1 tablespoon salt. Add beans, and cook until tender, about 2 minutes. Using a slotted spoon, transfer to ice-water bath to stop cooking. Drain well.
Add beans, carrots, and tomatoes to lettuces; toss to combine. Add 6 tablespoons dressing, and toss. Add more dressing to taste. Serve immediately.
You can use any variety of tender baby lettuce for this salad.