Finely chop the onions.

Wash the mixed salad greens well in a colander.

Mince the garlic.

Heat 1 tablespoon of oil in a large skillet over medium heat.

Add the chopped onions to the skillet and cook until softened and lightly browned, about 5-6 minutes.

Add the washed greens (with clinging water) to the skillet with the onions.

Season with salt and red pepper flakes to taste.

Sprinkle the minced garlic over the greens.

Cook, stirring frequently, until the greens are tender, about 5 minutes.

Remove the skillet from the heat.

Stir in the crumbled feta cheese.

Heat 2 teaspoons of oil on a griddle or in a large skillet over medium heat, spreading it evenly.

Place a corn tortilla on the heated griddle and cook on one side until softened, about 3 minutes.

Flip the tortilla to the other side.

Place 2-3 tablespoons of the greens and feta mixture in the center of the tortilla.

Sprinkle some mozzarella cheese over the greens and feta filling.

Use a spatula to fold the tortilla in half around the filling.

Cook until the tortilla is browned on one side, about 3 minutes.

Flip the quesadilla to the other side and cook until browned and the cheese is melted, about 3 minutes more.

Repeat the process until all tortillas and filling are used.

Serve immediately or keep warm in a 250-degree oven until all quesadillas are ready.