Border Knight Order's Cook!辺境騎士団のお料理係！, Henkyou Kishidan No Oryourigakari!

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/