1. Preheat the oven to 350 degrees and grease a 9x13 baking dish with nonstick cooking spray. 2. In a large bowl, mix together the cream of mushroom soup, milk, peas, cheese, tuna, salt, and pepper. 3. Add the cooked pasta and stir to coat. 4. Spread the mixture in the prepared baking dish. 5. Combine the melted butter and breadcrumbs in a small bowl, then sprinkle the mixture over the top of the casserole. 6. Bake in the preheated oven for 25 to 30 minutes, until the sauce is bubbly and the breadcrumbs are golden brown.