It is narrated from Humaid bin Abdur Rahman bin Awf that Umar and Uthman (may Allah be pleased with them) used to perform the Maghrib prayer when they saw the darkness of the night, and then after the prayer they would break their fast. This was during Ramadan.
Hadith Referenceمسند الإمام الشافعي / كتاب الصيام / 613
Hadith Takhrijاسناده ضعيف لإرساله اخرجه البيهقي : 4 / 238 ۔ وفي المعرفة السنن والآثار له (2506) ـ وعبدالرزاق (7588)۔