Make pie crust. Combine flour, salt, and sugar in a food processor. Add butter and pulse until the mixture resembles coarse meal, about 10 seconds.
Slowly add ice water, pulsing the mixture for no longer than 30 seconds, just until it begins to form a ball.
Divide dough ball into 2 pieces and place each on a piece of plastic wrap. Flatten into a disk, wrap in plastic, and refrigerate for at least 1 hour.
Remove dough from refrigerator.. Let the dough rest for several minutes at room temperature and then roll it out on a lightly floured surface until it fits a 9-inch pie plate. Transfer pie crust to pie plate. This is easy to do if you roll the dough on a piece of parchment paper and then just flip it over into the pie pan and peel the paper off.
Place tomato slices on paper towels to remove some of the excess moisture.
Preheat oven to 425 degrees.
In a medium bowl, mix together cheddar cheese, mayonnaise, parsley, green onions, Parmesan cheese, and bread crumbs.
Layer 1/2 of the tomatoes in the pie pan. Cover with 1/2 the cheese mixture. Repeat layers.
Bake for about 30 minutes or until top of the pie is browned and bubbling. Serve warm.