01 - Preheat oven to 375°F. Roll out the pie crust and press it into a 9-inch pie dish. Trim any overhang and flute the edges. Prick the bottom lightly with a fork to prevent puffing. Set aside.
02 - Heat olive oil in a large skillet over medium heat. Add the ground beef and cook, breaking it apart with a spoon, until browned and cooked through, about 5 to 7 minutes. Drain excess fat if needed.
03 - Add the diced onion and minced garlic to the skillet. Cook until softened, about 3 minutes. Stir in the marinara sauce, dried oregano, salt, and pepper. Bring to a simmer and cook for 5 minutes. Remove from heat.
04 - In a medium bowl, combine the ricotta cheese, egg, 1 cup of the mozzarella, Parmesan, basil, and red pepper flakes. Stir until smooth and well blended.
05 - Spread half of the meat sauce evenly over the bottom of the prepared crust. Dollop the ricotta mixture over the sauce and gently spread it into an even layer. Top with the remaining meat sauce, then sprinkle the remaining 1 cup of mozzarella over the top.
06 - Loosely tent the pie with aluminum foil. Bake for 30 minutes, then remove the foil and continue baking for 15 more minutes until the cheese is golden and bubbly.
07 - Let the pie cool for 10 minutes before slicing to allow the layers to set. Serve warm, garnished with fresh basil if desired.