Roughly chop the spinach.
Place olive oil and spinach in a skillet over medium heat.
Stir the spinach until it is just wilted. Remove from heat.
Place the spinach into a strainer over a bowl. Set aside while you work on the rest of the filling and the spinach releases the liquid.
Dice the onions and place into a bowl.
Add sumac, salt, lemon juice, pomegranate molasses, and pine nuts to the onions. Mix until everything is combined.
Remove the spinach from the strainer. It should be as dry as possible. (use paper towels to soak up excess liquid)
Add spinach to the onion mixture and stir until everything is incorporated.