This is so quick and easy to make and tastes like it took a long time to make. I got this recipe from Everyday Foods. The original recipe served 12 and made two pies, so I split the recipe to only make 1 pie.
Make the filling: In a large nonstick skillet, heat 2 tablespoons oil over medium-high heat. Add onions, and cook, stirring occasionally, until translucent, 3 to 5 minutes. Add garlic and 1 teaspoon salt; cook until garlic is tender, 1 to 2 minutes.
Transfer mixture to a large bowl; stir in spinach, feta, Parmesan, breadcrumbs, dill, 1 teaspoon salt, and ½ teaspoon pepper. Fold in eggs until combined.
Transfer mixture into a springform pan or a 9 ½-inch deep-dish pie plate; press firmly to flatten.
Make the topping: In a large bowl, gently toss sliced phyllo to separate, then toss with remaining 1/4 cup oil until coated.
Lay Phyllo on top of spinach mixture covering the top evenly and completely. (To freeze, cover pies tightly with plastic wrap, being careful not to flatten topping. Bake within 3 months; do not thaw first.).
Preheat oven to 375°. Bake until heated through and topping is golden brown, about 1 hour 15 minutes for frozen pie (30 minutes for unfrozen pie).