In a small bowl, toss the chopped spinach with a tiny squeeze of lemon juice and the dried oregano to wilt it slightly
Lay out the tortillas. On one half of each tortilla, layer a generous sprinkle of mozzarella, followed by the spinach, red onion slices, feta crumbles, and olives
Top with the remaining mozzarella and fold the tortilla in half to create a semi-circle
Heat a large non-stick skillet or griddle over medium heat. Brush the top of each folded tortilla lightly with olive oil
Place the quesadillas in the pan, oiled-side down. While the first side cooks, brush the now-top side with a bit more oil
Cook for 3–4 minutes per side until the tortilla is golden-brown and crispy, and the cheese is fully melted
While the quesadillas cook, whisk together the Greek yogurt, lemon juice, garlic powder, and herbs in a small ramekin
Remove from the pan and let rest for 1 minute. Slice each semi-circle into three triangles
Sprinkle with red pepper flakes for a hint of heat
Serve warm with the yogurt dipping sauce and a lemon wedge on the side
