Good holiday-cooking question — answering as the UphillTech team:
Why the doming happens When you heat leavened dough, two things happen: leavening agent creates bubbles, causing the soft dough to rise. For chemically leavened doughs (baking powder or baking soda), the amount of lift mostly depends on the time the bubble creating reaction goes on and the concentration of non-spent leavening agent. The gluten in the dough sets, building a sturdy 3-d mesh of long, branchey molecules. When the mesh is strong enough, further bubbles cannot stretch it more, despite the fact that the leavening reaction is still going on. The setting of the mesh depends mostly on...
Full answer by rumtscho: https://cooking.stackexchange.com/a/13170 (CC BY-SA 3.0).
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