Cut off top bud of asparagus spears and place in bowl. Chop rest of spears into 1/4" pieces ad add to bowl. Mix asparagus, olive oil, lemon juice and ¼ tsp. salt in bowl and allow to marinate. Add Greek yogurt, Italian dressing, mustard and pepper to bowl and stir well. Add artichokes, onion, tomatoes and potatoes and stir to coat.