Heat 2 tablespoons of olive oil in a large skillet over medium heat. Once shimmering, add 1 clove of minced garlic and sauté for about 30 seconds until fragrant.

Add 1 cup of roughly chopped fresh spinach to the skillet and cook for 2-3 minutes until wilted. Season with salt, pepper, 1 teaspoon of dried oregano, and optional red pepper flakes.

On a flat surface, lay out whole wheat tortillas and evenly distribute the spinach mixture on half of each tortilla.

Top with 1/2 cup of crumbled feta cheese, 1 cup of shredded mozzarella, and 1/4 cup of thinly sliced red onions.

Fold each tortilla over to create a half-moon shape and gently press to seal.

Return the skillet to medium heat, lightly coat it, and ensure it's hot.

Place the folded quesadillas in the skillet. Cook for 2-3 minutes until golden brown, then flip and cook for another 2-3 minutes until the cheese is melted.

Remove quesadillas from the skillet and let them rest for 1 minute on a cutting board.

Slice the quesadillas into wedges and serve warm with tzatziki or salad.