Preheat oven to 400°F. Cut tomatoes into ½-inch-thick slices. Place about 7 - 10 slices (depending on size of tomatoes but enough to cover top of pie) on a baking sheet lined with paper towels, and sprinkle with ¼ tsp. of the salt. Cover with additional paper towels and reserve.
Arrange remaining tomatoes in a single layer on a lightly greased wire rack on a large baking sheet. Sprinkle with ½ tsp. of the salt. Bake in the oven until wilted and slightly dried out about, 40 to 45 minutes. Cool completely, about 1 hour.
While cooling, cook bacon in a skillet over medium-high heat until fat is beginning to render about 4 to 5 minutes. Add chopped shallots and cook until bacon is crisp and shallots are carmelized about, 6 to 7 more minutes. Stir in garlic and cook until fragrant, about 1 minute. You do not want the garlic to burn. Using a slotted spoon, transfer the bacon mixture to a plate lined with paper towels to drain. Cool for 20 minutes.
Stir together cheese, mayonnaise, basil, Dijon mustard, and egg until combined. Sprinkle with pepper and remaining ¼ tsp. salt. Fold in bacon mixture.
Gently spread a third of cheese mixture onto the parmesan-buttermilk crust. Layer with half of the roasted tomato slices in a slightly overlapping pattern. Spread another third of cheese mixture on top of tomato slices. Repeat with remaining roasted tomato slices and cheese mixture. Top with reserved sliced fresh tomatoes, pressing filling gently into crust. Cover edges of pie with aluminum foil to keep from burning.
Bake in the oven at 400°F until filling is set, about 40-45 minutes. Transfer to a wire rack and let stand for 1 hour before serving. For added flavor, feel free to sprinkle freshly chopped basil on top before eating. Enjoy!