Preheat oven to 350F. Lightly grease a shallow 9" pie pan and set aside. Combine tofu through lemon in a blender and puree until smooth, stopping to scrape the sides as necessary. Continue to blend until the mixture is an even yellow and resembles a thick batter. Set batter aside. Line a skillet with 1/4 cup of water. Add mushrooms and saute over med-high heat. Once the mushrooms start to get soft, add thyme, basil and red pepper flakes and continue to cook until mushrooms are soft and the water has evaporated. Meanwhile, prepare frozen spinach according to packaging instructions, draining cooked spinach and pressing out any excess water. In a large bowl, mix tofu mixture with mushrooms and spinach. Once combined evenly, poor into preprared pie dish. Garnish with red bell pepper slices if desired and bake 30-45 minutes at 350, or until thoroughly warm and slighty crust at edges. Allow to cool for 15-20 minutes before slicing. The quiche should still be warm for serving but not piping hot.