Simple steamed spinach gets a refreshing topping of shaved vegetables to give it some crunch.
Prepare an ice-water bath. Place carrots, radishes, and beets in bath, and let stand for 20 minutes.
Whisk together oil, lemon juice, mustard, 1/2 teaspoon salt, and 1/4 teaspoon pepper. Stir in tarragon.
Cook spinach with water clinging to leaves, covered, in a large skillet over medium-high heat, stirring occasionally, until wilted, 3 to 5 minutes. Season with salt and pepper. Remove from skillet, and squeeze out excess liquid. Drizzle spinach with some of the dressing, toss, and arrange on a serving platter.
Using a slotted spoon, remove vegetables from ice-water bath, and transfer to a bowl. Add tomatoes. Toss with 3 to 4 tablespoons dressing. Arrange vegetables over spinach. Serve with remaining dressing on the side.
Shave the vegetables for this salad as thin as possible. If you don't have a handheld slicer, use a very sharp knife.