In English, the past tense of weak verbs* is formed by adding -ed. It the verb ends in e already, it is not doubled and the past tense is formed simply by adding -d. I respectfully submit that é is not e. Therefore the past tense of sauté is sautéed and the past tense of sautée is also sautéed.

*New verbs added to the language are correctly taken to be weak.