Using a citrus zester or a handheld fine grater, zest the navel orange and lemon. Place the zest in a small bowl and cover with boiling water. Let stand for 3 minutes; drain and scatter the zest strips on paper towels to dry. Set aside.
Working over a large bowl to catch any juice, peel the navel orange, lemon, blood orange, grapefruit, lime, and tangerines, removing all white pitch. Thinly slice each fruit crosswise and discard any seeds. Set the fruit slices aside.
To the collected fruit juices, whisk in the sugar, vinegar and oil. Set aside.
To arrange the salads, divide the mesclun among 6 large plates. Arrange the citrus slices on top in a decorative pattern, mixing the colors, sizes, and flavors.
In a small bowl. combine the shallots, basil, and walnuts; sprinkle the mixture over each salad. Again whisk the dressing and drizzle over each salad. Grind pepper on top and sprinkle with the reserved citrus zests. Serve at once.