Let piecrust stand at room temperature for 20 minutes. Gently press pastry into the bottom of pie plate and up the sides. Prick bottom of pastry. Line pastry with a double thickness of foil; bake 10 minutes. Remove foil; bake 5 minutes more. Remove, and reduce heat to 375 degrees F.
Cook onion in a little bacon fat or butter until softened, 5-10 min.
Sprinkle 1/2 cup of the cheese over the partially baked piecrust.
Halve 2 cups of the cherry tomatoes, leaving the remaining 2 cups whole. Place the halved and whole tomatoes in a large mixing bowl. Add olive oil, 2 Tbsp. of the basil, salt, and 1/4 tsp. of the pepper. Stir to combine. Add bacon pieces.
In a separate bowl beat together cream cheese, mayonnaise, egg yolk, cooked onion, lemon peel, and remaining Parmesan, basil, and pepper.
Spoon cream cheese mixture into piecrust. Top with tomato mixture. Gently press tomatoes and bacon into the cream cheese mixture.
Bake until tomatoes are just beginning to brown, about 35 minutes. Let stand 1 hour before cutting. Cut into wedges and top with lettuce to serve. Makes 6-8 servings