Begin by washing a generous amount of fresh spinach and chopping it roughly. Thinly slice half a red onion and grate equal parts of mozzarella and feta cheese until you have a good amount ready.

Take a tortilla and lay it flat on a clean surface. Layer a handful of spinach first, followed by crumbled feta, grated mozzarella, and sliced red onion. Top with another tortilla and gently press down to secure the filling.

Heat a non-stick skillet over medium heat, letting it warm up for 2-3 minutes. Add a drizzle of olive oil, then carefully place one prepared quesadilla in the skillet. Cook for about 3-5 minutes or until the bottom is golden brown and crispy. Flip using a spatula, adding a touch more oil if needed, then cook the other side for another 3-5 minutes until it is equally golden and the cheese is melty.

Once cooked to perfection, remove the quesadilla from the skillet and let it rest for a minute. Using a sharp knife or pizza cutter, slice it into wedges for serving.