Wilt spinach with salt, pepper, and nutmeg in skillet over medium heat (3–5 mins).
Squeeze out moisture from spinach using towel or strainer. Chop.
Mix spinach with garlic powder, red pepper, oregano, and half the mozzarella.
On each tortilla, layer mozzarella, spinach mix, feta, and more mozzarella. Fold in half.
Heat oil in pan on medium-low. Cook quesadillas 3–4 mins per side until crispy and golden.
Slice and serve with Greek yogurt or guac.