For the vinaigrette: In a medium bowl, combine the lemon juice, shallots, and garlic. Slowly whisk in the olive oil to form an emulsion. Add the chopped herbs. Stir in the diced tomatoes and Sweet 100's and mix well. Season with salt and pepper.
To assemble: On a round platter, arrange the sliced tomatoes in concentric circles, slightly overlapping the slices and alternating colors if using both red and yellow tomatoes. Season with salt and pepper.
Spoon the tomatoes from the vinaigrette over the sliced tomatoes, leaving some of the vinaigrette in the bowl. Toss the arugula in the bowl with the remaining vinaigrette. Season with salt and pepper. Arrange the arugula in the middle of the platter. Using a vegetable peeler, shave thin slices of Parmesan over the tomatoes and arugula. Pass freshly ground black pepper. Serve at room temperature.