Preheat the oven to 350 degrees F (175 degrees C). Coat a 2-quart casserole dish with cooking spray.

Cook egg noodles in a large pot of salted boiling water until al dente. Drain well.

Combine flour, butter, and salt in a medium saucepan over medium heat. Cook and stir until butter is melted and mixture is evenly combined. Gradually add milk; whisk until sauce thickens and begins to boil. Add cheese and whisk until melted and well combined. Stir in tuna, peas, and noodles. Spread mixture evenly in the prepared casserole dish.

Bake in the preheated oven until hot and bubbling, about 30 minutes.