TMZ reports, based on "sources with direct knowledge."
I had some trouble understanding the expression "bake-off," since there was no competition, only collusion, pretending to have found love together. But...
A big slice of the stunt involved Pamela claiming she was baking muffins and sourdough bread for Liam -- something he even played along with in interviews leading up to the premiere. It makes us now assume that was also part of the strategy ... pure role-play PR, not reality.
So some literal baking was involved, but there was no literal or figurative bake-off.
Actors promoting a movie are still acting. Why not act as if they'd fallen in love?
If you go searching into the term "bake-off," you'll probably quickly arrive at something called the "First Lady Bake-Off." That's something that began in 1992, and it was an unwholesome alliance between the press — Family Circle Magazine — and the Clinton campaign. Wikipedia explains: