Step 1: Prepare the Pan and Preheat Oven
Preheat the oven to 375°F (190°C). Lightly spray a 9-inch springform pan with oil to prevent sticking.

Step 2: Prepare the Spinach
Place thawed spinach in a strainer, rinse it, squeeze out as much moisture as possible, and pat dry with a paper towel. Finely chop the spinach and set aside.

Step 3: Make the Filling
In a large bowl, combine the cream cheese and chopped onion. Stir in the eggs, crumbled feta, chopped dill, salt, and nutmeg. Add the chopped spinach and mix well to combine.

Step 4: Layer the Phyllo Dough
Place 8 sheets of phyllo dough into the springform pan, one at a time, brushing each sheet with melted butter as you go. Rotate the sheets slightly to create a layered effect.

Step 5: Add the Filling
Pour the spinach and feta mixture into the phyllo shell. Smooth the top with a spatula.

Step 6: Garnish with Phyllo Roses
Brush the remaining 2 sheets of phyllo dough with butter, cut into 4 pieces, scrunch them into roses, and place them on top of the tart for decoration.

Step 7: Bake the Tart
Cover the tart loosely with foil and bake for 40 minutes. After 40 minutes, remove the foil and continue baking for another 20 minutes, or until golden and crispy.

Step 8: Serve
Allow the tart to cool for 5 minutes. Release the springform ring, slice into wedges, and serve with chives or green onions for garnish