For a smoky flavor, use a grill pan indoors or an outdoor grill to char the vegetables. Adjust the amount of jalapeno according to your spice preference. Remove the seeds and membranes for a milder flavor. Feel free to add other vegetables to the frittata, such as zucchini, corn, or bell peppers. If you don't have an oven-proof skillet, you can transfer the frittata to a greased baking dish before baking.