1. Preheat the oven to 375°F (190°C).
2. Wash and chop fresh spinach or thaw and drain frozen spinach.
3. In a pan, sauté chopped onions in olive oil until soft.
4. Add spinach to the pan and cook until wilted, then remove from heat.
5. In a bowl, mix crumbled feta cheese, beaten eggs, and chopped dill.
6. Combine the spinach mixture with the cheese and egg mixture.
7. Brush a baking dish with olive oil or melted butter.
8. Layer sheets of phyllo dough in the dish, brushing each with oil or butter.
9. Spread the spinach and feta filling evenly over the layered phyllo.
10. Cover with more layers of phyllo dough, brushing each with oil or butter.
11. Tuck in the edges and brush the top layer with extra oil or butter.
12. Score the top of the pie with a sharp knife to create portions.
13. Bake in the preheated oven for 40-50 minutes until golden brown and crispy.
14. Let the spanakopita cool slightly before slicing.
15. Serve warm or at room temperature and enjoy.