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 bubbling. Set aside.
02 - Heat olive oil in a large skillet over medium heat. Add ground beef and cook, breaking it apart with a spoon, until browned and no longer pink, about 5 to 7 minutes. Drain excess fat if needed.
03 - Add diced onion and minced garlic to the skillet. Sauté until softened, about 3 minutes. Stir in marinara sauce, dried oregano, salt, and pepper. Simmer for 5 minutes to blend flavors. Remove from heat.
04 - In a medium bowl, combine ricotta cheese, egg, 1 cup of mozzarella, Parmesan cheese, fresh basil, and red pepper flakes. Stir until smooth and well incorporated.
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 into an even layer. Top with the remaining meat sauce, then sprinkle the remaining 1 cup of mozzarella over the surface.
06 - Loosely tent the pie with aluminum foil. Bake for 30 minutes. Remove the foil and continue baking for an additional 15 minutes until the cheese is golden and bubbly.
07 - Allow the pie to cool for 10 minutes before slicing to set the layers. Serve warm, garnished with additional fresh basil if desired.