Slice the plum tomatoes into ¼ inch slices and place on doubled paper towels. Sprinkle each lightly with sea salt and press another paper towel on top. Let stand for 10 minutes.
Crumb topping: In a small mixing bowl, toss together bread crumbs, Parmesan, garlic and parsley with butter. Set aside.
Preheat oven to 350°F. Lightly spritz a 9-inch deep dish pie or tart pan with cooking spray. Fit the pie crust firmly into the pan and flute edges or press with the tines of a fork.
Meanwhile, In a medium stove top pot cook the macaroni in salted water per the instructions on the box until al dente. Drain well. Set aside to cool slightly, then add egg. Stir until coated.
To make cheese sauce: In a 2 quart saucepan, melt butter over medium-high heat. Add flour, Dijon salt and onion powder. Whisk until combined then cook on low for 1 minute.
Gradually add milk, whisking constantly. After all of the milk has been incorporated, bring the mixture to a boil, stirring constantly. Lower the heat immediately, and let the mixture slowly bubble for 3-5 minutes until it's thickened. Stir periodically to avoid sticking.
Add 1 cup each of the grated Havarti and sharp white cheddar cheese. Stir until melted.
Remove the cheese sauce from the heat and add to the cooked macaroni-egg mixture. Mix until evenly coated.
Spread the macaroni and cheese evenly into pie shell. Top with ½ of the remaining shredded cheese.
Arrange the tomato slices on top of the cheese, sprinkling with remaining ½ cup cheese. Sprinkle buttered crumbs on top.
Bake for 35-40 minutes. Allow pie to stand for 10 minutes then, cut and serve.