Spray a stainless steel (or other not non-stick) saucepan or small frying pan lightly with the vegetable or olive oil cooking spray. Set the pan over medium heat and let it get hot for a minute before adding the carrots and chili powder. Stir well and often and cook until the carrots are tender, about 2 minutes, depending on how coarsely shredded the carrots are.
Add the salsa, black beans, and frozen corn. Stir, reduce the heat to low, and cook until the beans and corn are both hot all the way through and the corn reaches desired tenderness, about 5 minutes.
If desired, line each tortilla with a lettuce leaf. Divide the bean and corn filling evenly between the tortillas, then do the same with the cheese. Scatter fresh cilantro (or parsley or shredded lettuce) leaves over the top. Fold in half, then in half again to form a triangle. Serve warm or at room temperature.
The original recipe calls for shredded lettuce and sour cream. While you can certainly substitute the lettuce for the herb, I prefer the burst of freshness that cilantro or parsley provides.
By all means, add sour cream if you want. I like it just as well without (or with Greek yogurt) and it keeps the price down. If you have it on hand and want to use it, though, it will taste wonderful!