Marion Cunningham, a former California homemaker who overcame agoraphobia later in life to become one of America’s most famous and enthusiastic advocates of home cooking, died on Wednesday in Walnut Creek, Calif. She was 90.

Mrs. Cunningham, who had Alzheimer’s disease, was admitted to the John Muir Medical Center on Tuesday with respiratory problems, John Carroll, a family friend, said in confirming the death. She had been living at an assisted-care home in Walnut Creek, the small Bay Area city where she had raised her family.

“More than anyone else, she gave legitimacy to home cooking,” Michael Bauer, the executive food editor of The San Francisco Chronicle, said of Mrs. Cunningham. “She took what many people would say was housewife food and really gave it respect by force of her own personality.”

Mrs. Cunningham’s most enduring trait may have been her ability to make even novice cooks feel as if they could accomplish something in the kitchen. Indeed, she took many of them under her wing and drew from them for her popular book “Learning to Cook.”