In a small bowl, add finely minced shallot or onion and vinegar. Let shallot marinate in the vinegar for 10 minutes to mellow the harsh onion flavor while you prepare remaining ingredients.
Cut the top and bottom from oranges then remove peel using a paring knife. Remove as much of the white pith as possible without taking too much of the flesh. Cut orange into ¼" slices and then cut slices in half and set aside.
Finish the orange vinaigrette by adding Dijon mustard, salt, orange marmalade and orange juice to the vinegar/shallot mixture. Whisk to combine then continue to whisk while slowly drizzling in the olive oil. Once the dressing has formed an emulsion, give it a taste and season with additional salt and pepper as desired.
Assemble salad on a serving plate or bowl by layering the arugula with the orange slices, pomegranate and toasted walnuts. Drizzle the dressing lightly over the salad, sprinkle with a sprinkling of coarse salt and fresh cracked pepper, serve immediately and enjoy!
Keep the red dye from pomegranates from staining your clothes by submerging the fruit in a colander under water and peeling the seeds while submerged.