Following package directions, thaw phyllo dough. You will only be using 1/2 the package for this recipe - about 16 sheets depending on the brand used.
Preheat oven to 350ºF.
In a small bowl, whisk together olive oil and melted butter. Heat 2-3 Tbsp. of the oil-butter mixture in a large sauté pan. Add scallions, onions and dill. Cook over medium-high heat until onions are soft and almost transparent. Add thawed, drained spinach and cook about 3 minutes. Mix in garlic and cook for an additional minute. Remove pan from heat and drain off any excess liquid; set aside to cool.
In a large bowl, combine eggs, lemon juice, ricotta, feta, Parmesan cheeses, and black pepper. Fold into spinach mixture. (Note: Adding salt is not necessary as the Feta cheese is rather salty.)
Unroll and cover phyllo sheets with plastic wrap, then a slightly dampened towel to prevent sheets from drying out.
Grease the bottom and sides of a 9”x13” baking pan. Using one sheet of dough at a time, lay it in the pan and lightly brush with oil-butter mixture. Continue covering each sheet with another until you have used half the amount of phyllo sheets. Remember to keep remaining dough covered.
Spread all of the spinach-cheese mixture evenly over the bottom stack of phyllo sheets.
Follow the same procedure of layering and brushing the oil-butter mixture on each of the remaining sheets of dough. Be sure the spinach-cheese mixture is completely covered with phyllo and that any overhanging phyllo is tucked-in around the edge of the baking pan. Generously brush the top layer with oil-butter mixture.
With a sharp knife, cut the spinach pie into 8 or 12 squares.
Bake for 45- 50 minutes or until the top is golden brown. Let sit for 10 - 15 minutes before serving.
Serve with a tossed salad and a dollop of plain yogurt, if desired