01 - Preheat oven to 375°F. Roll out the pie crust and gently press it into a 9-inch pie dish. Trim any overhang and flute the edges decoratively. 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 wooden spoon, until evenly browned and no pink remains, approximately 5 to 7 minutes. Drain excess fat if needed.
03 - Add the diced onion and minced garlic to the skillet. Sauté until softened and fragrant, about 3 minutes. Stir in the marinara sauce, dried oregano, salt, and pepper. Bring to a gentle simmer and cook for 5 minutes to meld the flavors. Remove from heat.
04 - In a medium mixing bowl, combine the ricotta cheese, egg, 1 cup of the mozzarella, Parmesan, chopped basil, and red pepper flakes. Stir until smooth, creamy, and evenly blended.
05 - Spread half of the meat sauce evenly across 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 evenly over the surface.
06 - Loosely tent the pie with aluminum foil. Bake for 30 minutes, then carefully remove the foil and continue baking for an additional 15 minutes, or until the cheese is deeply golden and bubbling.
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.