Heat oven to 450°F. Prepare pie crust as directed on package for one-crust baked shell using 10-inch springform pan or 9-inch glass pie pan. Spread mustard over bottom of crust. Bake at 450°F. for 9 to 11 minutes or until crust is light golden brown. Reduce oven temperature to 350°F.
Meanwhile, melt butter in large skillet over medium-low heat. Add spinach, onion and tomatoes; cook 5 to 7 minutes or until onion is crisp-tender, stirring frequently. Remove from heat. Add Italian seasoning, oregano, garlic powder and salt; mix well.
Beat eggs in large bowl until well blended. Add spinach mixture and cheese; mix well. Spoon filling evenly into partially baked shell. Sprinkle pine nuts evenly over top, pressing in slightly.
Bake at 350°F. for 25 to 35 minutes or until filling and pine nuts are golden brown. Let stand 10 minutes before serving.