In a mixing bowl, combine spinach, mozzarella, feta, tomato, red onion, and black pepper.

Lay one tortilla flat and spread one-quarter of the filling over half of it.

Fold the tortilla over to cover the filling completely.

Heat a large skillet over medium heat and add olive oil.

Place the filled tortilla in the pan and cook for about 3–4 minutes until golden brown.

Flip the quesadilla carefully and cook the other side until it’s also golden and the cheese melts.

Remove from heat and let it cool slightly so the cheese sets.

Slice into wedges and serve warm with your favorite sides.