Cook Spinach According To Package Directions For Microwave; Drain And Squeeze Dry. Set Aside. Place Onion And Butter In A Small Microwave-Safe Bowl. Cover And Microwave At 70% Power For 2-3 Minutes Or Until Onion Is Tender, Stirring Once; Set Aside. In A Large Bowl, Beat Cream Cheese And Whipping Cream Until Smooth. Fold In The Spinach, Artichokes, Cheeses, Cayenne, Pepper And Onion Mixture. Transfer To A Greased 9-In. Microwave-Safe Pie Plate. Sprinkle With Parmesan Cheese. Microwave, Uncovered, On High For 4-5 Minutes Or Until Bubbly. Serve With Crackers.