Add the flour, sugar and salt to a food processor and pulse just until combined.
In a small bowl, whisk together the egg, vinegar and water.
Add the cold butter pieces into the food processor and pulse until small coarse crumbs remain.
Sprinkle the water/egg mixture over the flour and pulse again until the dough comes together.
Remove the dough with your hands and wrap it in plastic wrap. Refrigerate the dough for 30 minutes. After 30 minutes, roll the dough out and place it in a 9-inch tart pan or (deep dish) pie plate.
Preheat the oven to 350 degrees F.
Whisk together the eggs, garlic, cream, cheese, pimento cheese, herbs, onions and a big pinch of salt and pepper. Pour the filling into the crust. Brush the edges of the crust with the egg wash. Sprinkle the edges with everything seasoning.
Bake for 55 to 60 minutes, or until golden on top and set in the center. Let cool slightly before serving. This is so good served warm or cold! I like to serve it with a greens salad.