Can consuming 2.5x the recommended daily serving of red meat be harmful if only eat red meat once a fortnight / once a month?

Many things possible: Many things are possible in this world, so the answer to the question, "Can something happen...," is usually YES. Eating that small amount of red meat can be harmful (anything's possible) but only in very unusual circumstances. For the vast majority of people, eating red meat 1-2 times each month is not harmful at all. If not eating red meat, one should be sure to get iron from other sources.