Bring a large pot of lightly salted water to a boil.
Cook pasta in boiling water for 8 to 10 minutes, or until al dente; drain.
Pour pasta back in pot.
Preheat oven to 425 F (220 C).
Add the onion, cheddar cheese, peas, tuna, soup, milk, and pepper to the pasta.
Mix thoroughly.
Transfer to a 9x13 inch baking dish.
Sprinkle top with garlic bread crumbs and romano cheese.
Bake for 15 minutes or until bread crumbs start to brown and casserole starts to bubble.
Notes:
* I made garlic bread crumbs from leftover garlic bread without cheese that I forgot in the oven and it dried up. I crushed it in the blender. Using up the garlic bread was actually the reason for making a tuna casserole. For those interested,