1-First, gather and prepare all ingredients by washing vegetables, chopping the tomato, spinach, and red onion to the right sizes, and crumbling the feta cheese. Preheat a non-stick skillet over medium heat and lightly oil it to get started.

2-Next, assemble the quesadilla by spreading the mixture evenly over one half of each of the three burrito-style flour tortillas. Include the diced tomato, red onion, chopped spinach, feta cheese, shredded mozzarella cheese, and pepper to taste, then fold each in half for a neat package.

3-Now, cook the quesadillas in the prepared pan over medium heat for 3-4 minutes per side until the cheese melts beautifully. After cooking, let them rest for 5 minutes to set, making slicing easier.

4-Finally, slice each quesadilla into 3 or 4 pieces and serve warm with optional toppings like sour cream, salsa, or pico de gallo. This whole process takes about 15 minutes, proving it’s perfect for busy lifestyles, and you can adapt it for vegan or gluten-free needs as mentioned.