In a heatproof serving bowl in the middle of the oven, heat butter until melted, about 5 minutes. Remove from oven.
Cook ravioli in 4 quarts of water for each pound. Add a hearty pinch of salt. Bring water to a full boil, reduce heat and then add ravioli. (If you add ravioli when the water is at a robust boil, you risk having the ravioli split open.) Occasionally, stir gently to prevent ravioli from sticking to the bottom of the pot. Once water returns to a gentle boil, cook about 8-12 minutes. Drain carefully, or simply use a slotted spoon to remove the ravioli individually from the pot. Reserve 1/2 cup of ravioli cooking water.
Add ravioli to butter and salt in bowl, then slowly add 3/4 cup cheese, tossing gently and adding enough of cooking water to keep ravioli moist. Season with salt and pepper to taste, then sprinkle with remaining cheese.