01 - Preheat oven to 375°F. Roll out the pie crust and fit it into a 9-inch pie dish. Trim and flute the edges. Prick the bottom gently with a fork and set aside.
02 - In a large skillet over medium heat, warm the olive oil. Add 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. Simmer for 5 minutes, then remove from heat.
04 - In a medium bowl, combine the ricotta cheese, egg, 1 cup of the mozzarella, Parmesan, basil, and red pepper flakes. Mix until smooth and creamy.
05 - Spread half of the meat sauce evenly over 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 - Allow the pie to cool for 10 minutes before slicing to let the layers set. Serve warm, garnished with additional fresh basil if desired.