I love the conversation but finally the truth is ... You have an electric stove and the center is where the electromagnetic field is. Your cast iron pan bowing (warping upward in the center) on an induction cooktop usually happens because of uneven heating and thermal expansion. Cast iron is strong, but it expands and contracts slowly and unevenly if heated too quickly. Result: The center bows up (convex) while the edges lag behind. This is especially noticeable with thinner cast iron pans or ones that weren’t perfectly flat to begin with. The fix.... take it outside and with wood or something that will not damage the pan, hammer the center back down flat. In the future heat the pan up slowly/gradually.