Melt butter in a large skillet over medium heat. Add onions and cook, stirring often, until softened and lightly browned, about 10 minutes.
Stir in thyme, oregano, pepper, and salt. Reduce heat to low and cook, stirring occasionally, until onions are golden brown and caramelized, about 30 minutes.
Line a 9-inch pie plate with one of the pie crusts. Spoon onion mixture into the crust.
Top with remaining pie crust, pressing the edges of the crusts together to seal. Cut several vents in the top crust.
Bake in preheated oven until crust is golden brown, about 30 minutes.
Cool for 10 minutes before serving.
Interesting Facts
Onions are a great source of fiber, Vitamin C, and antioxidants.
Caramelizing onions gives them a sweet flavor which is perfect for this pie.
This pie is great served with a side salad for a complete meal.