Cain (again) lives up to expectations. He understands that you should not live past God. He is going to answer God through the bringing of a gift: a sacrifice. Hebrews 11:4 shows that Abel’s sacrifice had added value through his faith.
That does not mean Cain did not believe. Cain takes some of the fruits of his daily labour. He gives that back to God, as it were. It is reminiscent of the lesson of the later Psalm 127:1–5.
3 Au bout de quelque temps, Caïn fit à l'Eternel une offrande des fruits de la terre;