In a 5-quart stove-top pot, bring water to a boil. Add pasta and hold at a boil until tender (usually once water starts to boil turn heat down to medium heat and let cook for ten minutes). Then turn off the heat and drain pasta in the 5-quart pot.
Add tuna, peas, and can of soup. Stir gently to not break the pasta. Pour mixture into a 9x12-inch baking dish or an 8x8 baking dish. Distribute cheese evenly over the pasta mix.
At this point, you can let it cool and cover it after 20 minutes, refrigerate and prepare for dinner the following evening, or put it directly into a 350°F oven and bake uncovered for 30 minutes.
Carefully remove from oven with hot mitts and serve. Can be served alone or with hot bread and a green salad.