Prep Ingredients: Wash 2 cups of spinach, pat dry, and chop. Slice 1 medium red onion and crumble 1 cup of feta cheese. Gather 2 cups of shredded mozzarella and tortillas.

Sauté Onions: Heat 2 tablespoons of olive oil in a skillet over medium heat. Add sliced red onion and sauté for about 5 minutes until translucent.

Combine Filling: In a mixing bowl, combine sautéed onions with chopped spinach, crumbled feta, and shredded mozzarella. Toss until combined.

Assemble Quesadillas: Lay out 2 tortillas, spoon filling on one, and top with the second tortilla. Press down gently.

Cook Quesadillas: In the skillet, cook quesadilla on medium-low heat for 3-4 minutes. Flip and cook for another 3-4 minutes until crispy.

Serve: Let cool, slice into wedges, and serve warm, optionally with parsley or tzatziki.