If you prefer a burrito with a milder taste, use jalapeno peppers, which are slightly larger and cooler than serrano chiles.
In a medium bowl, combine tomato, cucumber, avocado, chile, cilantro, lime juice, and mayonnaise. Season with salt and pepper. Divide mixture among the four tortillas; roll up. Cut each tortilla in half; serve with the Chile-Rubbed Salmon and Black Beans and Corn.