Start by washing and slicing your vegetables. Thinly slice the red onion, avocado, and tomatoes. Drain the roasted red bell peppers and set them aside.
In a small mixing bowl, combine the mayonnaise and Sriracha. Stir until well blended.
Take one slice of hearty wheat bread and spread 2 tablespoons of basil pesto evenly over it.
On top of the pesto, layer the baby spinach, sliced tomatoes, avocado, red onion, and roasted red pepper strips. Sprinkle the crumbled feta cheese over the top.
Sprinkle a little salt and pepper over the stacked ingredients. Spread the Sriracha mayo on one side of the second slice of bread and place it mayo-side down on top of the layered ingredients.
If you enjoy a crispy sandwich, heat a sandwich press or grill pan over medium heat. Grill the sandwich for 2-3 minutes on each side until golden brown and crispy.
Once your Mediterranean Sandwich is assembled and toasted (if desired), slice it in half diagonally. Serve it immediately for the best taste experience!