Turning Off Gas Stove on Yom Tov

Question

I have seen a couple quick responses to people saying that turning off a gas stove on Yom Tov is permitted because it is not kibui. Rather, it is cutting off the supply of gas, thereby causing the flame to go out. Despite this explanation, my spouse is still skeptical, never having seen anyone do it, and wants to learn the source(s). I have heard that this is also how Rav Moshe poskened. Can you please let me know where to look? Thank you.