Spray a large skillet with cooking spray; warm over medium-high heat. Whisk eggs together in a bowl. Pour into the skillet. Add spinach, green onions, garlic salt, and Cajun seasoning. Cook and stir until eggs are nearly set, about 5 minutes.
Pour black beans into a small pot over medium heat. Cook, stirring occasionally, until heated through, about 5 minutes.
Sprinkle Mexican cheese blend over tortillas. Place tortillas on microwave-safe plates or paper towels. Microwave 2 tortillas at a time, about 30 minute seconds. Repeat with remaining tortillas.
Divide egg mixture and beans over the center of the tortillas. Top with salsa and sour cream.