Heat oven to 350 degrees Fahrenheit (180 degrees Celsius). Line a 10-inch (26-centimeter) round pan or a 9- x 13-inch (20- x 30-centimeter) baking pan with Gefen Parchment Paper.

Place one phyllo sheet in the pan. Grease it well with butter or cooking spray. Cover with another phyllo sheet and repeat with remaining sheets.

For the filling, sauté onion in olive oil until golden, about 10 minutes.

Add garlic and spinach leaves. Season with salt and pepper and stir gently while cooking, about five minutes, or until spinach loses its volume.

Transfer mixture to a strainer to drain the excess liquid, then transfer to a bowl. Add remaining filling ingredients and mix well.

Pour spinach mixture onto phyllo base. Sprinkle with feta cubes and sundried tomatoes. Bake about 40 minutes or until golden.