PREHEAT OVEN TO 450F. Butter a 9-by-13-inch oven-proof glass or earthenware casserole dish. Make an incision along the length of each bell pepper and remove the stem, seeds and membranes, keeping the peppers whole. Fill a medium-size saucepan or skillet halfway with water and bring it to a boil. Add the peppers, let the water return to a boil and cook until the peppers are just softened, about 3 minutes. Remove and blot them very dry with paper towels. Let them cool completely and then line the bottom of the casserole with them. Separate the eggs into 2 large bowls. Beat the yolks until smooth, then stir in the cheese, corn, milk, jalapeno peppers and salt and black pepper. Whisk the whites until soft peaks form, then fold them into the yolk mixture, gently stirring just until almost blended. Scrape the mixture into the prepared dish and transfer it to the middle rack of the preheated oven. Bake just until the eggs are puffy and the top is lightly browned, about 7 minutes. Reduce the heat to 325F and continue cooking until the eggs are baked through but not dry, 22 to 25 minutes. Test by inserting a knife into the center. It should come out almost clean. Remove the pan and let it sit for a few minutes before cutting the casserole into 12 rectangles. Serve each portion with some salsa spooned on top.