During Amavasyai, if the food is not ready for Perumal Tiruvaradhanam, can we perform Pitru tharpanam and then proceed to do Tiruvaradhanam?

During Amavasyai, whatever food is ready one can offer it to Perumal, complete Tiruvaradhanam and proceed to perform vaivashvadevam, tharpanam and then offer the remaining food to Perumal.