Nanchatte Cinderella: Oukyuu Inbou-hen - Isekai de, Outaishihi Hajimemashita.

Maya Izumi, a 33 year old professional pastry chef, went out to buy some mustard when she got caught in an accident. When she had regained her awareness, she had reincarnated as a 12 year old princess! And she also had a husband who was older than her (and also the crown prince)! Maya, realizing that she seems to have had been reincarnated in a place where her life is in danger, decides to try to get along with her husband to protect herself! In the name of being a pastry chef, she'll defeat the criminal and her husband's stomach at the same time! (Source: Kadokawa, translated)