1.In A Skillet, Saute Onion And Green Pepper In 1 Teaspoon Oil Until Almost Tender. Add Mushrooms; Cook 2-3 Minutes Longer. Remove And Keep Warm. 2.In The Same Skillet, Lightly Brown One Tortilla In 1/2 Teaspoon Oil. Turn Over; Top With Half Of The Pepperoni, Tomatoes, Onion Mixture And Cheese. Cover And Cook Until Cheese Is Melted, About 2 Minutes. Sprinkle With Pepper Flakes If Desired. Repeat For Second Pizza.