Prepare the sauce - in a small saucepan, whisk the almond milk and cornstarch together until smooth. Place over medium heat and stir until it just begins to thicken. Reduce the heat to low and stir in the Parmesan cheese, garlic powder, onion powder, salt, and pepper until melted and smooth.
Turn off the heat and set aside. The sauce will thicken more as it sits.
Spray a frying pan with cooking spray and heat over medium heat. Add one tortilla and cook 2-3 minutes on each side. Repeat with the second tortilla. This will help crisp up the tortilla, preventing it from getting soggy.
Heat a skillet over medium heat and spray with cooking spray. Sauté onions and peppers until softened. Add steak slices and cook until just browned. Remove from heat.
Spread 2 tablespoons of the white cheese sauce evenly on each tortilla. Top with steak, peppers, and onions. Sprinkle mozzarella cheese on top.