1) Roast red peppers over a flame. If you have a gas stove, you can stick them right on the flame or you can grill them. You can also just used jarred peppers. Cook them until they are nicely charred all the way around.
2) Add peppers to a bowl and cover with plastic wrap. Let rest for 10 minutes and then peel off pepper skins. It’s okay if some skin is left on.
3) Dice peppers and sun-dried tomatoes.
4) Cook macaroni according to package.
5) For cheese sauce, add butter and flour to a medium pan over medium heat. Whisk together once butter has melted to form a roux. Cook for about 3 minutes, whisking constantly.
6) Slowly add milk to the roux, starting with just a few tablespoons. Whisk it constantly so no lumps form. Keep adding milk in small increments until all your milk is added and your sauce is silky smooth. Turn your heat down to medium-low and continue to cook it until it thickens.
7) Whisk in cheeses into the sauce and season with salt and pepper.
8) Drain pasta and mix with peppers and tomatoes, then stir in cheese sauce.
9) Add macaroni to a buttered baking dish (2.5 quart or 9×13). Top with bread crumbs and bake for 30-35 minutes at 350 degrees.
10) Let cool briefly before serving.