Add potatoes and 1 tsp. salt to medium saucepan. Add enough water to cover potatoes and bring to a boil over high heat. Reduce heat and simmer 7-10 minutes, or until potatoes are tender.

Drain potatoes and let cool 30 minutes.

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.

Serve immediately on bed of spinach or cover and refrigerate up to 24 hours before serving.