Preheat the oven to 350 degrees and set a large ovenproof skillet or frying pan over medium heat. Whisk together the eggs, milk, basil, and 1/3 cup of the parmesan cheese in a medium sized bowl along with a big pinch of salt. Set aside.

Add the olive oil and butter to the skillet. Once the butter melts and begins to bubble/foam, add the shallot and a pinch of salt. Cook 1-2 minutes until softened and translucent, then add the serrano pepper if using and cook for an additional minute before adding the corn kernels and another pinch of salt. Cook 2-3 minutes, stirring regularly. Spread the corn, shallot, and peppers into an even layer on the bottom of the pan, then pour the egg mixture over the top. Arrange the tomatoes on top of the eggs then sprinkle with the remaining 1/3 cup parmesan cheese. Once you see the eggs just starting to set around the edges of the skillet and bubbles starting to sputter up from the bottom (this should happen within about 5 minutes), transfer the skillet to the middle rack of the preheated oven. Bake the frittata for 10-15 minutes or until the eggs are just set. 

Allow the frittata to cool for 5-10 minutes then slice and serve. Or, transfer it to a platter then slice and serve. Garnish with additional basil and parmesan if desired. 

Keep leftovers in the fridge and make sure to enjoy within 4-5 days. Leftovers can be reheated in the air fryer or oven.