Cover the casserole dish tightly with aluminum foil to trap the moisture. This is important so the noodles absorb the liquid and become tender instead of drying out.
Bake, covered, in the preheated oven for 35–40 minutes, until the noodles are tender when you poke a fork down into the center and the sauce is hot and bubbly.
Carefully remove the foil (watch for steam), then return the uncovered casserole to the oven and bake for an additional 10–15 minutes, or until the top is lightly golden and the cheese has melted into a creamy layer.
Remove the casserole from the oven and let it rest for about 5–10 minutes before serving. This short rest helps the sauce thicken slightly and makes it easier to scoop neat portions.
Spoon the savory French onion noodles onto plates or into bowls, making sure each serving gets some of the creamy sauce from the bottom of the dish. Serve warm.
