Using a food processor, pulse together the flour and salt until combined. Add butter and pulse until mixture becomes coarse meal, about 15 pulses.
In a small bowl, combine egg and water. Add the egg mixture to food processor and pulse until it starts to clump together. DO NOT pulse until a ball is formed. It should be crumbly with large clumps of dough.
Turn dough only a lightly floured surface and form into a ball. Flatten slightly to form a disk. Wrap in plastic wrap and put in fridge for at least 1 hour or up to 3 days.
Preheat oven to 350°F. Once ready, remove dough from the fridge about 10 minutes before you begin rolling. On a lightly floured surface, roll the dough so that it is about 3 inches longer than you pie dish and is between ⅛ inch and ¼ inch in thickness.
Press the dough into the bottom and along the sides of the pie plate, being careful not to puncture the dough. Use kitchen scissors to trim the dough overhang to about 1 ½ inches. Fold over and flute the edges. Place in fridge while cooking the veggies.
Heat olive oil in a large skillet over medium heat. Add the zucchini, broccoli and pepper and cook for 5 minutes. Remove from heat and stir in garlic, green onions and tomato.
Evenly spread 1 ½ cups cheddar cheese across bottom of pie crust. Add the veggie mixture. In a large bowl, whisk together the eggs, milk, salt and black pepper. Pour evenly over everything. Top with remaining ½ cup cheese.
Bake for 40-55 minutes or until the middle is just slightly jiggly. You can use a cake tester to test as well. You might need to cover crust with aluminum foil if it's starting to brown to quickly. Remove from oven and let sit for 15 minutes so it sets. (This is very important. If you don't let it sit for 15 minutes it will break up as you slice.)