Sauté the spinach: In a large skillet, heat a tablespoon of olive oil over medium heat. Add the minced garlic and cook for about 30 seconds until fragrant. Add the fresh spinach in batches and cook until it’s fully wilted. This should take about 3-5 minutes.

Squeeze out the moisture: Transfer the wilted spinach to a strainer or a bowl lined with paper towels. Press down with a spatula or your hands to squeeze out as much excess water as you can.

Mix the filling: In a medium bowl, combine the drained spinach with the crumbled feta cheese and diced tomatoes. Add any optional melting cheese and season with a little black pepper and maybe some red pepper flakes if you like a little heat.

Assemble the quesadilla: Wipe out the skillet and add a little more oil or butter. Place one tortilla in the pan. On one half of the tortilla, sprinkle some of the melting cheese, then add a generous layer of the spinach and feta mixture. Top with a final sprinkle of cheese.

Fold and cook: Fold the empty half of the tortilla over the filling, pressing down gently with your spatula. Cook for 2-3 minutes per side, until the tortilla is golden brown and the cheese is melted and bubbly.

Serve: Remove from the pan, slice into wedges, and serve immediately with your favorite toppings.