Make it gluten free: Use certified gluten-free corn tortillas.
Make it dairy free: Substitute mild extra-virgin olive oil for the butter, water or neutral non-dairy milk for the sour cream, and omit the cheese and any dairy toppings. Vegan sour cream would be nice on top, but so would guacamole or avocado.
Vegetable note: Try to slice your veggies into similarly sized, narrow pieces so they cook at the same rate. Vegetable options include cabbage, bell pepper, carrot, onion, zucchini or yellow squash, Brussels sprouts, etc. More dense vegetables like butternut squash or sweet potato will probably require a longer cooking time.
Change it up: You can stretch out this recipe to yield 6 hearty tacos by adding ½ cup cooked beans to the egg mixture before cooking. I love pinto beans, and black beans are good, too. You’ll need a couple more tortillas for this variation, naturally.