Thaw the pastry at room temperature for 40 minutes. Heat the oven to 375 degrees F.
Heat the oil in a 10-inch skillet over medium heat. Add the onions and cook until they're tender. Add the garlic and cook for 1 minute. Add the spinach and cook until the liquid evaporates. Remove the skillet from heat and let it cool.
Beat the soup, eggs and dill weed in a medium bowl. Stir in the cheese and spinach mixture.
Unfold the pastry on a lightly floured surface. Roll into a 13 x 9-inch rectangle. Place it in a 13 x 9-inch baking pan. Top with the spinach mixture. Roll out the remaining pastry sheet and place it over the spinach mixture. Cut 4 slits in the top of the pastry.