In a large mixing bowl, combine the all-purpose flour, salt, sugar, and instant yeast.

Add warm water and vegetable oil to the dry ingredients, and mix until a dough forms.

Knead the dough on a lightly floured surface for about 5 minutes, until smooth and elastic.

Place the dough in a greased bowl, cover with a towel, and let it rise for 1 hour, or until doubled in size.

While the dough is rising, prepare the filling. In a skillet, cook the ground beef and onion until the beef is browned and the onion is soft.

Add the chopped spinach, cumin, sumac, salt, and black pepper to the skillet. Cook for another 5 minutes, until the spinach wilts.

Preheat the oven to 375°F (190°C).

Divide the risen dough into 8 equal portions. Roll out each portion into a circle with a diameter of about 6 inches.

Place a spoonful of the beef and spinach filling in the center of each dough circle. Fold the edges of the dough over the filling, pinching them together to seal.

Arrange the fatayer on a baking sheet lined with parchment paper. Bake for 20 minutes, or until golden brown.

Serve the beef and spinach fatayer warm as an appetizer or snack.