Śatapatha Brāhmaṇa ("of a hundred paths") 3.8.2.26

3.8.2.26

athājyamupastṛṇīte | atha hiraṇyaśakalamavadadhātyatha vapāmavadyannāhāgnīṣomābhyāṃ cāgasya vapāyai medaso 'nubrūhītyatha hiraṇyaśakalamavadadhātyathopariṣṭāddvirājyasyābhighārayati

Thereupon he makes an 'underlayer' of ghee (in the guhû-spoon), and lays a piece of gold thereon. Then, cutting off the omentum (from the spits and putting it into the spoon), he says (to the Hotri), 'Recite (the invitatory prayer) to Agni and Soma for the omentum and fat of the buck!' He then lays (another) piece of gold on (the omentum) and bastes it twice with ghee above.