Blind bake the pie crust at 350 degrees for approximately 15 minutes, or until just starting to brown using pie weights or beans.
Chop the tomatoes and place in a colander in the sink sprinkled with a bit of salt, to allow liquid to drain.
Meanwhile, saute onion in oil in a medium skillet on medium high until browned (2-3 minutes). Add spinach and turn the heat to medium- saute until wilted and most of the liquid has evaporated (5-7 minutes). Season with salt, pepper, and crushed red pepper.
Meanwhile, mix together mayonnaise, mozzarella, hot sauce, and salt and pepper to taste in a small bowl.
Pat tomatoes dry with a paper towel and add to spinach mixture.
Spread the spinach mixture in the half baked pie crust and top with mayo mixture.
Bake at 350 for 35-40 minutes, or until browned and bubbly.
Allow to sit for at least 10 minutes before cutting into the pie.