Henkyou Kishidan no Oryourigakari! Suterare Youjo desu ga, Kahogo na Kazoku ni Hirowarete Oishii Gohan wo Tsukurimasu

After being abandoned by her biological father, El suddenly remembers her past life.
She is taken in by a frontier count’s family and comes to live alongside the frontier knight order.
There’s Lars, a master swordsman; Merlino, a healing mage; and Halon, who strives to catch up to and surpass his older brothers.
The three brothers are overjoyed to have a new little sister—and dote on her endlessly.
However… the food in the frontier region is terribly bad.
So begins the reincarnated little girl’s culinary reform!

https://www.cmoa.jp/title/346100/