Wash and slice the tomatoes and place on a paper towel lined plate to drain.
Heat the olive oil in a large skillet over medium heat. Add the zucchini in a single layer, season with salt and pepper and cook until lightly browned. Remove to a plate and add the onion to the hot skillet. Cook for just a few minutes or until lightly browned but still crips. Add the cooked onions to the zucchini and set aside.
In a medium mixing bowl combine the eggs, half-and-half, flour, chopped basil, salt, pepper, cayenne and dry mustard. Whisk until well blended or make it super easy and hit it with an immersion blender.
Sprinkle the shredded cheese in the bottom of the baked crust. Layer half the tomatoes and zucchini over the cheese. Gently pour the egg mixture over the vegetables. Top with the remaining tomatoes, zucchini and onions.
Sprinkle with paprika and bake for 30 minutes or until the egg mixture is set in the center. Tent the quiche with aluminum foil during baking if the crust browns too quickly.
Remove from the oven and allow the quiche to cool for 10-15 minutes before serving. It may also be served at room temperature. Garnish with fresh basil if desired.
Store leftovers in an airtight container in the refrigerator.