。
My mother prepared lunch for me.
Literal
Mother [topic-は] me [for-に] lunch [possessive-の] preparation [object-を] did-[benefactive-てくれた]
昼食の準備をしてくれた = 'did the preparation of lunch (for me).' 昼食 (ちゅうしょく) is the formal/written word for lunch — the everyday spoken counterpart is お昼ごはん or ランチ. ~てくれる marks the action as done for the speaker's benefit, a small but warm grammatical detail that English captures only loosely with 'for me.'