Preheat oven to 275 degrees.
Season salmon with salt and pepper. Combine ¼ cup fresh orange juice with ¼ cup lemon juice, 2 tablespoon olive oil, 1 tablespoon whole grain mustard, 1 tablespoon honey, 2 tablespoon minced shallots, and 1 teaspoon minced garlic. Pour half of the marinade on the salmon, reserving the other half. Marinate the salmon for 20 minutes.
Place the salmon in a baking dish and roast with the skin side down for 40-50 minutes.
Meanwhile, slice ½ an orange paper-thin. Heat 1 tablespoon oil in a saute and pan and arrange the orange slices in one even layer. Cook over medium-high heat until caramelized. Flip the orange slices and caramelize on the other side. Remove from heat and set aside.
Remove the salmon from the oven. Pour the reserved marinade on top and garnish with the caramelized orange and fresh dill. Serve immediately.